SQL
Interview Questions with Answers
What is RDBMS?
Relational
Data Base Management Systems (RDBMS) are database management systems that
maintain
data
records and indices in tables. Relationships may be created and maintained
across and among the
data
and tables. In a relational database, relationships between data items are
expressed by means of
tables.
Interdependencies among these tables are expressed by data values rather than
by pointers.
This
allows a high degree of data independence. An RDBMS has the capability to
recombine the data
items
from different files, providing powerful tools for data usage.
What is
normalization?
Database
normalization is a data design and organization process applied to data
structures based on
rules
that help build relational databases. In relational database design, the
process of organizing data
to
minimize redundancy. Normalization usually involves dividing a database into
two or more tables and
defining
relationships between the tables. The objective is to isolate data so that
additions, deletions,
and
modifications of a field can be made in just one table and then propagated
through the rest of the
database
via the defined relationships.
What
are different normalization forms?
1NF:
Eliminate Repeating Groups
Make a
separate table for each set of related attributes, and give each table a
primary key. Each field
contains
at most one value from its attribute domain.
2NF:
Eliminate Redundant Data
If an
attribute depends on only part of a multi-valued key, remove it to a separate
table.
3NF:
Eliminate Columns Not Dependent On Key
If
attributes do not contribute to a description of the key, remove them to a
separate table. All
attributes
must be directly dependent on the primary key
BCNF:
Boyce-Codd Normal Form
If
there are non-trivial dependencies between candidate key attributes, separate
them out into distinct
tables.
4NF:
Isolate Independent Multiple Relationships
No
table may contain two or more 1:n or n:m relationships that are not directly
related.
5NF:
Isolate Semantically Related Multiple Relationships
There
may be practical constrains on information that justify separating logically
related many-to-many
relationships.
ONF:
Optimal Normal Form
A model
limited to only simple (elemental) facts, as expressed in Object Role Model
notation.
DKNF:
Domain-Key Normal Form
A model
free from all modification anomalies.
Remember,
these normalization guidelines are cumulative. For a database to be in 3NF, it
must first
fulfill
all the criteria of a 2NF and 1NF database.
What is
Stored Procedure?
A
stored procedure is a named group of SQL statements that have been previously
created and stored
in the
server database. Stored procedures accept input parameters so that a single
procedure can be
used
over the network by several clients using different input data. And when the
procedure is
modified,
all clients automatically get the new version. Stored procedures reduce network
traffic and
improve
performance. Stored procedures can be used to help ensure the integrity of the
database.
e.g.
sp_helpdb, sp_renamedb, sp_depends etc.
What is
Trigger?
A
trigger is a SQL procedure that initiates an action when an event (INSERT,
DELETE or UPDATE)
occurs.
Triggers are stored in and managed by the DBMS.Triggers are used to maintain
the referential
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integrity
of data by changing the data in a systematic fashion. A trigger cannot be
called or executed;
the
DBMS automatically fires the trigger as a result of a data modification to the
associated table.
Triggers
can be viewed as similar to stored procedures in that both consist of
procedural logic that is
stored
at the database level. Stored procedures, however, are not event-drive and are
not attached to a
specific
table as triggers are. Stored procedures are explicitly executed by invoking a
CALL to the
procedure
while triggers are implicitly executed. In addition, triggers can also execute
stored
procedures.
Nested
Trigger: A trigger can also contain INSERT, UPDATE and DELETE logic within
itself, so when the
trigger
is fired because of data modification it can also cause another data
modification, thereby firing
another
trigger. A trigger that contains data modification logic within itself is
called a nested trigger.
What is
View?
A
simple view can be thought of as a subset of a table. It can be used for
retrieving data, as well as
updating
or deleting rows. Rows updated or deleted in the view are updated or deleted in
the table the
view
was created with. It should also be noted that as data in the original table
changes, so does data
in the
view, as views are the way to look at part of the original table. The results
of using a view are
not
permanently stored in the database. The data accessed through a view is
actually constructed using
standard
T-SQL select command and can come from one to many different base tables or
even other
views.
What is
Index?
An
index is a physical structure containing pointers to the data. Indices are
created in an existing table
to
locate rows more quickly and efficiently. It is possible to create an index on
one or more columns of
a
table, and each index is given a name. The users cannot see the indexes, they
are just used to speed
up
queries. Effective indexes are one of the best ways to improve performance in a
database
application.
A table scan happens when there is no index available to help a query. In a
table scan SQL
Server
examines every row in the table to satisfy the query results. Table scans are
sometimes
unavoidable,
but on large tables, scans have a terrific impact on performance.
Clustered
indexes define the physical sorting of a database table’s rows in the storage
media. For this
reason,
each database table may have only one clustered index.
Non-clustered
indexes are created outside of the database table and contain a sorted list of
references
to the
table itself.
What is
the difference between clustered and a non-clustered index?
A
clustered index is a special type of index that reorders the way records in the
table are physically
stored.
Therefore table can have only one clustered index. The leaf nodes of a
clustered index contain
the
data pages.
A
nonclustered index is a special type of index in which the logical order of the
index does not match
the
physical stored order of the rows on disk. The leaf node of a nonclustered
index does not consist of
the
data pages. Instead, the leaf nodes contain index rows.
What
are the different index configurations a table can have?
A table
can have one of the following index configurations:
No
indexes
A
clustered index
A
clustered index and many nonclustered indexes
A
nonclustered index
Many
nonclustered indexes
What is
cursors?
Cursor
is a database object used by applications to manipulate data in a set on a
row-by-row basis,
instead
of the typical SQL commands that operate on all the rows in the set at one
time.
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In
order to work with a cursor we need to perform some steps in the following
order:
Declare
cursor
Open
cursor
Fetch
row from the cursor
Process
fetched row
Close
cursor
Deallocate
cursor
What is
the use of DBCC commands?
DBCC stands
for database consistency checker. We use these commands to check the
consistency of
the
databases, i.e., maintenance, validation task and status checks.
E.g.
DBCC CHECKDB - Ensures that tables in the db and the indexes are correctly
linked.
DBCC
CHECKALLOC - To check that all pages in a db are correctly allocated.
DBCC
CHECKFILEGROUP - Checks all tables file group for any damage.
What is
a Linked Server?
Linked
Servers is a concept in SQL Server by which we can add other SQL Server to a
Group and query
both
the SQL Server dbs using T-SQL Statements. With a linked server, you can create
very clean, easy
to
follow, SQL statements that allow remote data to be retrieved, joined and
combined with local data.
Storped
Procedure sp_addlinkedserver, sp_addlinkedsrvlogin will be used add new Linked
Server.
What is
Collation?
Collation
refers to a set of rules that determine how data is sorted and compared.
Character data is
sorted
using rules that define the correct character sequence, with options for specifying
casesensitivity,
accent
marks, kana character types and character width.
What
are different type of Collation Sensitivity?
Case
sensitivity
A and
a, B and b, etc.
Accent
sensitivity
a and
á, o and ó, etc.
Kana
Sensitivity
When
Japanese kana characters Hiragana and Katakana are treated differently, it is
called Kana
sensitive.
Width
sensitivity
When a
single-byte character (half-width) and the same character when represented as a
double-byte
character
(full-width) are treated differently then it is width sensitive.
What's
the difference between a primary key and a unique key?
Both
primary key and unique enforce uniqueness of the column on which they are
defined. But by
default
primary key creates a clustered index on the column, where are unique creates a
nonclustered
index
by default. Another major difference is that, primary key doesn't allow NULLs,
but unique key
allows
one NULL only.
How to
implement one-to-one, one-to-many and many-to-many relationships while
designing
tables?
One-to-One
relationship can be implemented as a single table and rarely as two tables with
primary
and
foreign key relationships.
One-to-Many
relationships are implemented by splitting the data into two tables with
primary key and
foreign
key relationships.
Many-to-Many
relationships are implemented using a junction table with the keys from both
the tables
forming
the composite primary key of the junction table.
What is
a NOLOCK?
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Using
the NOLOCK query optimiser hint is generally considered good practice in order
to improve
concurrency
on a busy system. When the NOLOCK hint is included in a SELECT statement, no
locks are
taken
when data is read. The result is a Dirty Read, which means that another process
could be
updating
the data at the exact time you are reading it. There are no guarantees that
your query will
retrieve
the most recent data. The advantage to performance is that your reading of data
will not block
updates
from taking place, and updates will not block your reading of data. SELECT
statements take
Shared
(Read) locks. This means that multiple SELECT statements are allowed
simultaneous access, but
other
processes are blocked from modifying the data. The updates will queue until all
the reads have
completed,
and reads requested after the update will wait for the updates to complete. The
result to
your
system is delay(blocking).
What is
difference between DELETE & TRUNCATE commands?
Delete
command removes the rows from a table based on the condition that we provide
with a WHERE
clause.
Truncate will actually remove all the rows from a table and there will be no
data in the table
after
we run the truncate command.
TRUNCATE
TRUNCATE
is faster and uses fewer system and transaction log resources than DELETE.
TRUNCATE
removes the data by deallocating the data pages used to store the table’s data,
and only the
page
deallocations are recorded in the transaction log.
TRUNCATE
removes all rows from a table, but the table structure and its columns,
constraints, indexes
and so
on remain. The counter used by an identity for new rows is reset to the seed
for the column.
You
cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint.
Because
TRUNCATE TABLE is not logged, it cannot activate a trigger.
TRUNCATE
can not be Rolled back.
TRUNCATE
is DDL Command.
TRUNCATE
Resets identity of the table.
DELETE
DELETE
removes rows one at a time and records an entry in the transaction log for each
deleted row.
If you
want to retain the identity counter, use DELETE instead. If you want to remove
table definition
and its
data, use the DROP TABLE statement.
DELETE
Can be used with or without a WHERE clause
DELETE
Activates Triggers.
DELETE
Can be Rolled back.
DELETE
is DML Command.
DELETE
does not reset identity of the table.
Difference
between Function and Stored Procedure?
UDF can
be used in the SQL statements anywhere in the WHERE/HAVING/SELECT section where
as
Stored
procedures cannot be.
UDFs
that return tables can be treated as another rowset. This can be used in JOINs
with other tables.
Inline
UDF's can be though of as views that take parameters and can be used in JOINs
and other
Rowset
operations.
When is
the use of UPDATE_STATISTICS command?
This
command is basically used when a large processing of data has occurred. If a
large amount of
deletions
any modification or Bulk Copy into the tables has occurred, it has to update
the indexes to
take
these changes into account. UPDATE_STATISTICS updates the indexes on these
tables
accordingly.
What
types of Joins are possible with Sql Server?
Joins
are used in queries to explain how different tables are related. Joins also let
you select data from
a table
depending upon data from another table.
Types
of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further
classified as LEFT
OUTER
JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.
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What is
the difference between a HAVING CLAUSE and a WHERE CLAUSE?
Specifies
a search condition for a group or an aggregate. HAVING can be used only with
the SELECT
statement.
HAVING is typically used in a GROUP BY clause. When GROUP BY is not used, HAVING
behaves
like a WHERE clause. Having Clause is basically used only with the GROUP BY
function in a
query.
WHERE Clause is applied to each row before they are part of the GROUP BY
function in a query.
What is
sub-query? Explain properties of sub-query.
Sub-queries
are often referred to as sub-selects, as they allow a SELECT
statement to be executed
arbitrarily
within the body of another SQL statement. A sub-query is executed by enclosing
it in a set of
parentheses.
Sub-queries are generally used to return a single row as an atomic value,
though they
may be
used to compare values against multiple rows with the IN keyword.
A
subquery is a SELECT statement that is nested within another T-SQL statement. A
subquery SELECT
statement
if executed independently of the T-SQL statement, in which it is nested, will
return a result
set.
Meaning a subquery SELECT statement can standalone and is not depended on the
statement in
which
it is nested. A subquery SELECT statement can return any number of values, and
can be found
in, the
column list of a SELECT statement, a FROM, GROUP BY, HAVING, and/or ORDER BY
clauses of a
T-SQL
statement. A Subquery can also be used as a parameter to a function call.
Basically a subquery
can be
used anywhere an expression can be used.
Properties
of Sub-Query
A
subquery must be enclosed in the parenthesis.
A
subquery must be put in the right hand of the comparison operator, and
A
subquery cannot contain a ORDER-BY clause.
A query
can contain more than one sub-queries.
What
are types of sub-queries?
Single-row
subquery, where the subquery returns only one row.
Multiple-row
subquery, where the subquery returns multiple rows,.and
Multiple
column subquery, where the subquery returns multiple columns.
What is
SQL Profiler?
SQL
Profiler is a graphical tool that allows system administrators to monitor
events in an instance of
Microsoft
SQL Server. You can capture and save data about each event to a file or SQL
Server table to
analyze
later. For example, you can monitor a production environment to see which
stored procedures
are
hampering performance by executing too slowly.
Use SQL
Profiler to monitor only the events in which you are interested. If traces are
becoming too
large,
you can filter them based on the information you want, so that only a subset of
the event data is
collected.
Monitoring too many events adds overhead to the server and the monitoring
process and can
cause
the trace file or trace table to grow very large, especially when the
monitoring process takes
place over
a long period of time.
What is
User Defined Functions?
User-Defined
Functions allow to define its own T-SQL functions that can accept 0 or more
parameters
and
return a single scalar data value or a table data type.
What
kind of User-Defined Functions can be created?
There
are three types of User-Defined functions in SQL Server 2000 and they are
Scalar, Inline Table-
Valued
and Multi-statement Table-valued.
Scalar
User-Defined Function
A
Scalar user-defined function returns one of the scalar data types. Text, ntext,
image and timestamp
data
types are not supported. These are the type of user-defined functions that most
developers are
used to
in other programming languages. You pass in 0 to many parameters and you get a
return
value.
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Inline
Table-Value User-Defined Function
An
Inline Table-Value user-defined function returns a table data type and is an
exceptional alternative
to a
view as the user-defined function can pass parameters into a T-SQL select
command and in
essence
provide us with a parameterized, non-updateable view of the underlying tables.
Multi-statement
Table-Value User-Defined Function
A
Multi-Statement Table-Value user-defined function returns a table and is also
an exceptional
alternative
to a view as the function can support multiple T-SQL statements to build the
final result
where
the view is limited to a single SELECT statement. Also, the ability to pass parameters
into a TSQL
select
command or a group of them gives us the capability to in essence create a
parameterized,
non-updateable
view of the data in the underlying tables. Within the create function command
you
must
define the table structure that is being returned. After creating this type of
user-defined function,
It can
be used in the FROM clause of a T-SQL command unlike the behavior found when
using a stored
procedure
which can also return record sets.
Which
TCP/IP port does SQL Server run on? How can it be changed?
SQL
Server runs on port 1433. It can be changed from the Network Utility TCP/IP
properties –> Port
number.both
on client and the server.
What
are the authentication modes in SQL Server? How can it be changed?
Windows
mode and mixed mode (SQL & Windows).
To
change authentication mode in SQL Server click Start, Programs, Microsoft SQL
Server and click SQL
Enterprise
Manager to run SQL Enterprise Manager from the Microsoft SQL Server program
group.
Select
the server then from the Tools menu select SQL Server Configuration Properties,
and choose the
Security
page.
Where
are SQL server users names and passwords are stored in sql server?
They
get stored in master db in the sysxlogins table.
Which
command using Query Analyzer will give you the version of SQL server and
operating
system?
SELECT
SERVERPROPERTY('productversion'), SERVERPROPERTY ('productlevel'),
SERVERPROPERTY
('edition')
What is
SQL server agent?
SQL
Server agent plays an important role in the day-to-day tasks of a database
administrator (DBA). It
is
often overlooked as one of the main tools for SQL Server management. Its
purpose is to ease the
implementation
of tasks for the DBA, with its full-function scheduling engine, which allows
you to
schedule
your own jobs and scripts.
Can a
stored procedure call itself or recursive stored procedure? How many level SP
nesting
possible?
Yes.
Because Transact-SQL supports recursion, you can write stored procedures that
call themselves.
Recursion
can be defined as a method of problem solving wherein the solution is arrived
at by
repetitively
applying it to subsets of the problem. A common application of recursive logic
is to perform
numeric
computations that lend themselves to repetitive evaluation by the same
processing steps.
Stored
procedures are nested when one stored procedure calls another or executes
managed code by
referencing
a CLR routine, type, or aggregate. You can nest stored procedures and managed code
references
up to 32 levels.
What is
@@ERROR?
The
@@ERROR automatic variable returns the error code of the last Transact-SQL
statement. If there
was no
error, @@ERROR returns zero. Because @@ERROR is reset after each Transact-SQL
statement,
it must
be saved to a variable if it is needed to process it further after checking it.
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What is
Raiseerror?
Stored
procedures report errors to client applications via the RAISERROR command.
RAISERROR
doesn't
change the flow of a procedure; it merely displays an error message, sets the
@@ERROR
automatic
variable, and optionally writes the message to the SQL Server error log and the
NT
application
event log.
What is
log shipping?
Log
shipping is the process of automating the backup of database and transaction
log files on a
production
SQL server, and then restoring them onto a standby server. Enterprise Editions
only
supports
log shipping. In log shipping the transactional log file from one server is
automatically updated
into
the backup database on the other server. If one server fails, the other server
will have the same db
can be
used this as the Disaster Recovery plan. The key feature of log shipping is
that is will
automatically
backup transaction logs throughout the day and automatically restore them on
the
standby
server at defined interval.
What is
the difference between a local and a global variable?
A local
temporary table exists only for the duration of a connection or, if defined
inside a compound
statement,
for the duration of the compound statement.
A
global temporary table remains in the database permanently, but the rows exist
only within a given
connection.
When connection are closed, the data in the global temporary table disappears.
However,
the
table definition remains with the database for access when database is opened
next time.
What
command do we use to rename a db?
sp_renamedb
‘oldname’ , ‘newname’
If
someone is using db it will not accept sp_renmaedb. In that case first bring db
to single user using
sp_dboptions.
Use sp_renamedb to rename database. Use sp_dboptions to bring database to multi
user
mode.
What is
sp_configure commands and set commands?
Use
sp_configure to display or change server-level settings. To change
database-level settings, use
ALTER
DATABASE. To change settings that affect only the current user session, use the
SET statement.
What
are the different types of replication? Explain.
The SQL
Server 2000-supported replication types are as follows:
· Transactional
· Snapshot
· Merge
Snapshot
replication distributes data exactly as it appears at a specific moment in time
and does not
monitor
for updates to the data. Snapshot replication is best used as a method for
replicating data that
changes
infrequently or where the most up-to-date values (low latency) are not a
requirement. When
synchronization
occurs, the entire snapshot is generated and sent to Subscribers.
Transactional
replication, an initial snapshot of data is applied at Subscribers, and then
when data
modifications
are made at the Publisher, the individual transactions are captured and
propagated to
Subscribers.
Merge
replication is the process of distributing data from Publisher to Subscribers,
allowing the
Publisher
and Subscribers to make updates while connected or disconnected, and then
merging the
updates
between sites when they are connected.
What
are the OS services that the SQL Server installation adds?
MS SQL
SERVER SERVICE, SQL AGENT SERVICE, DTC (Distribution transac co-ordinator)
What
are three SQL keywords used to change or set someone’s permissions?
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GRANT,
DENY, and REVOKE.
What
does it mean to have quoted_identifier on? What are the implications of having
it off?
When
SET QUOTED_IDENTIFIER is ON, identifiers can be delimited by double quotation
marks, and
literals
must be delimited by single quotation marks. When SET QUOTED_IDENTIFIER is OFF,
identifiers
cannot
be quoted and must follow all Transact-SQL rules for identifiers.
What is
the STUFF function and how does it differ from the REPLACE function?
STUFF
function to overwrite existing characters. Using this syntax,
STUFF(string_expression, start,
length,
replacement_characters), string_expression is the string that will have
characters substituted,
start
is the starting position, length is the number of characters in the string that
are substituted, and
replacement_characters
are the new characters interjected into the string.
REPLACE
function to replace existing characters of all occurance. Using this syntax
REPLACE(string_expression,
search_string, replacement_string), where every incidence of
search_string
found in the string_expression will be replaced with replacement_string.
Using
query analyzer, name 3 ways to get an accurate count of the number of records
in a
table?
SELECT
* FROM table1
SELECT
COUNT(*) FROM table1
SELECT
rows FROM sysindexes WHERE id = OBJECT_ID(table1) AND indid < 2
How to
rebuild Master Database?
Shutdown
Microsoft SQL Server 2000, and then run Rebuildm.exe. This is located in the
Program
Files\Microsoft
SQL Server\80\Tools\Binn directory.
In the
Rebuild Master dialog box, click Browse.
In the
Browse for Folder dialog box, select the \Data folder on the SQL Server 2000
compact disc or in
the
shared network directory from which SQL Server 2000 was installed, and then
click OK.
Click
Settings. In the Collation Settings dialog box, verify or change settings used
for the master
database
and all other databases.
Initially,
the default collation settings are shown, but these may not match the collation
selected during
setup.
You can select the same settings used during setup or select new collation
settings. When done,
click
OK.
In the
Rebuild Master dialog box, click Rebuild to start the process.
The
Rebuild Master utility reinstalls the master database.
To
continue, you may need to stop a server that is running.
Source:
http://msdn2.microsoft.com/en-us/library/aa197950(SQL.80).aspx
What is
the basic functions for master, msdb, model, tempdb databases?
The
Master database holds information for all databases located on the SQL Server
instance and is the
glue
that holds the engine together. Because SQL Server cannot start without a
functioning master
database,
you must administer this database with care.
The
msdb database stores information regarding database backups, SQL Agent
information, DTS
packages,
SQL Server jobs, and some replication information such as for log shipping.
The
tempdb holds temporary objects such as global and local temporary tables and
stored procedures.
The
model is essentially a template database used in the creation of any new user
database created in
the
instance.
What
are primary keys and foreign keys?
Primary
keys are the unique identifiers for each row. They must contain unique values
and cannot be
null.
Due to their importance in relational databases, Primary keys are the most
fundamental of all keys
and
constraints. A table can have only one Primary key.
Foreign
keys are both a method of ensuring data integrity and a manifestation of the
relationship
between
tables.
What is
data integrity? Explain constraints?
Data
integrity is an important feature in SQL Server. When used properly, it ensures
that data is
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accurate,
correct, and valid. It also acts as a trap for otherwise undetectable bugs
within applications.
A
PRIMARY KEY constraint is a unique identifier for a row within a database
table. Every table should
have a
primary key constraint to uniquely identify each row and only one primary key
constraint can be
created
for each table. The primary key constraints are used to enforce entity
integrity.
A
UNIQUE constraint enforces the uniqueness of the values in a set of columns, so
no duplicate values
are
entered. The unique key constraints are used to enforce entity integrity as the
primary key
constraints.
A
FOREIGN KEY constraint prevents any actions that would destroy links between
tables with the
corresponding
data values. A foreign key in one table points to a primary key in another
table. Foreign
keys
prevent actions that would leave rows with foreign key values when there are no
primary keys
with
that value. The foreign key constraints are used to enforce referential
integrity.
A CHECK
constraint is used to limit the values that can be placed in a column. The
check constraints
are
used to enforce domain integrity.
A NOT
NULL constraint enforces that the column will not accept null values. The not
null constraints
are
used to enforce domain integrity, as the check constraints.
What
are the properties of the Relational tables?
Relational
tables have six properties:
· Values are atomic.
· Column values are of the same kind.
· Each row is unique.
· The sequence of columns is insignificant.
· The sequence of rows is insignificant.
· Each column must have a unique name.
What is
De-normalization?
De-normalization
is the process of attempting to optimize the performance of a database by
adding
redundant
data. It is sometimes necessary because current DBMSs implement the relational
model
poorly.
A true relational DBMS would allow for a fully normalized database at the
logical level, while
providing
physical storage of data that is tuned for high performance. De-normalization
is a technique
to move
from higher to lower normal forms of database modeling in order to speed up
database access.
How to
get @@error and @@rowcount at the same time?
If
@@Rowcount is checked after Error checking statement then it will have 0 as the
value of
@@Recordcount
as it would have been reset.
And if
@@Recordcount is checked before the error-checking statement then @@Error would
get reset.
To get
@@error and @@rowcount at the same time do both in same statement and store
them in local
variable.
SELECT @RC = @@ROWCOUNT, @ER = @@ERROR
What is
Identity?
Identity
(or AutoNumber) is a column that automatically generates numeric values. A
start and
increment
value can be set, but most DBA leave these at 1. A GUID column also generates
numbers,
the
value of this cannot be controled. Identity/GUID columns do not need to be
indexed.
What is
a Scheduled Jobs or What is a Scheduled Tasks?
Scheduled
tasks let user automate processes that run on regular or predictable cycles.
User can
schedule
administrative tasks, such as cube processing, to run during times of slow
business activity.
User
can also determine the order in which tasks run by creating job steps within a
SQL Server Agent
job.
E.g. Back up database, Update Stats of Tables. Job steps give user control over
flow of execution.
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If one
job fails, user can configure SQL Server Agent to continue to run the remaining
tasks or to stop
execution.
What is
a table called, if it does not have neither Cluster nor Non-cluster Index? What
is it
used
for?
Unindexed
table or Heap. Microsoft Press Books and Book On Line (BOL) refers it as Heap.
A heap
is a table that does not have a clustered index and, therefore, the pages are
not linked by
pointers.
The IAM pages are the only structures that link the pages in a table together.
Unindexed
tables are good for fast storing of data. Many times it is better to drop all
indexes from table
and
than do bulk of inserts and to restore those indexes after that.
What is
BCP? When does it used?
BulkCopy
is a tool used to copy huge amount of data from tables and views. BCP does not
copy the
structures
same as source to destination.
How do
you load large data to the SQL server database?
BulkCopy
is a tool used to copy huge amount of data from tables. BULK INSERT command
helps to
Imports
a data file into a database table or view in a user-specified format.
Can we
rewrite subqueries into simple select statements or with joins?
Subqueries
can often be re-written to use a standard outer join, resulting in faster
performance. As we
may
know, an outer join uses the plus sign (+) operator to tell the database to
return all non-matching
rows
with NULL values. Hence we combine the outer join with a NULL test in the WHERE
clause to
reproduce
the result set without using a sub-query.
Can SQL
Servers linked to other servers like Oracle?
SQL
Server can be lined to any server provided it has OLE-DB provider from
Microsoft to allow a link.
E.g.
Oracle has a OLE-DB provider for oracle that Microsoft provides to add it as
linked server to SQL
Server
group.
How to
know which index a table is using?
SELECT
table_name,index_name FROM user_constraints
How to
copy the tables, schema and views from one SQL server to another?
Microsoft
SQL Server 2000 Data Transformation Services (DTS) is a set of graphical tools
and
programmable
objects that lets user extract, transform, and consolidate data from disparate
sources
into
single or multiple destinations.
What is
Self Join?
This is
a particular case when one table joins to itself, with one or two aliases to
avoid confusion. A self
join
can be of any type, as long as the joined tables are the same. A self join is
rather unique in that it
involves
a relationship with only one table. The common example is when company have a
hierarchal
reporting
structure whereby one member of staff reports to another.
What is
Cross Join?
A cross
join that does not have a WHERE clause produces the Cartesian product of the
tables involved
in the
join. The size of a Cartesian product result set is the number of rows in the
first table multiplied
by the
number of rows in the second table. The common example is when company wants to
combine
each
product with a pricing table to analyze each product at each price.
Which
virtual table does a trigger use?
Inserted
and Deleted.
List
few advantages of Stored Procedure.
· Stored procedure can reduced network traffic and latency, boosting
application performance.
· Stored procedure execution plans can be reused, staying cached in SQL
Server's memory,
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reducing
server overhead.
· Stored procedures help promote code reuse.
· Stored procedures can encapsulate logic. You can change stored
procedure code without
affecting
clients.
· Stored procedures provide better security to your data.
What is
DataWarehousing?
· Subject-oriented, meaning that the data in the database is organized
so that all the data
elements
relating to the same real-world event or object are linked together;
· Time-variant, meaning that the changes to the data in the database are
tracked and recorded
so that
reports can be produced showing changes over time;
· Non-volatile, meaning that data in the database is never over-written
or deleted, once
committed,
the data is static, read-only, but retained for future reporting;
· Integrated, meaning that the database contains data from most or all
of an organization's
operational
applications, and that this data is made consistent.
What is
OLTP(OnLine Transaction Processing)?
In OLTP
- online transaction processing systems relational database design use the
discipline of data
modeling
and generally follow the Code rules of data normalization in order to ensure
absolute data
integrity.
Using these rules complex information is broken down into its most simple
structures (a table)
where
all of the individual atomic level elements relate to each other and satisfy
the normalization
rules.
How do
SQL server 2000 and XML linked? Can XML be used to access data?
FOR XML
(ROW, AUTO, EXPLICIT)
You can
execute SQL queries against existing relational databases to return results as
XML rather than
standard
rowsets. These queries can be executed directly or from within stored
procedures. To retrieve
XML
results, use the FOR XML clause of the SELECT statement and specify an XML mode
of RAW, AUTO,
or
EXPLICIT.
OPENXML
OPENXML
is a Transact-SQL keyword that provides a relational/rowset view over an
in-memory XML
document.
OPENXML is a rowset provider similar to a table or a view. OPENXML provides a
way to
access
XML data within the Transact-SQL context by transferring data from an XML
document into the
relational
tables. Thus, OPENXML allows you to manage an XML document and its interaction
with the
relational
environment.
What is
an execution plan? When would you use it? How would you view the execution
plan?
An
execution plan is basically a road map that graphically or textually shows the
data retrieval methods
chosen
by the SQL Server query optimizer for a stored procedure or ad-hoc query and is
a very useful
tool
for a developer to understand the performance characteristics of a query or
stored procedure since
the
plan is the one that SQL Server will place in its cache and use to execute the
stored procedure or
query.
From within Query Analyzer is an option called "Show Execution Plan"
(located on the Query
drop-down
menu). If this option is turned on it will display query execution plan in
separate window
when query is ran again.
For futher information, more questions and answers, please do visit
www.sqlauthority.com
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
C# Interview Questions and Answers
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
C# Interview Questions and Answers
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
http://www.aired.in/2009/11/c-sharp-interview-questions-answers.html Or http://www.authorcode.com/c-sharp-interview-questions-and-answers/ Or http://www.careerride.com/CSharp-Interview-Questions.aspx Or http://www.globalguideline.com/interview_questions/Questions.php?sc=C_Sharp_Programming_Language_Interview_Questions_A
CompTIA A+
Pop Quiz Archive
Questions and Answers
SAMPLE
This is a sample archive of the daily CompTIA A+ daily pop quiz that is hosted on http://www.rejictschools.blogsot.com Each
weekday, we send a pop-quiz question to our user community to help them prepare for their CompTIA A+ certification
exam. We hope this compilation will provide you with the information you’ll need to get CompTIA A+ certified.
Our entire library of free CompTIA A+ videos can always be found at http://www.FreeAPlus.com. If you like this taste of
our archive, then you’ll love the entire set. Learn more about our downloadable pop quiz archive athttp://www.rejictschools.blogsot.com
You’d like to use the command line to connect to a Windows share on your central file server. Which command can be
used at a command prompt to connect to a network share?
A) NET CONNECT
B) SHARE USE
C) SHARE CONNECT
D) NET USE
E) O HAI CONNECT THE SHARE PLZ
The answer: D) NET USE
The NET USE command can be used at the command line to connect to a share.
Question 10-202
You need to automate file transfer to occur every morning at 3am. What Windows utility would be a good choice to use
for this requirement?
A) Task Scheduler
B) Task Manager
C) Program Manager
D) Windows Calendar
E) Coffee Maker
The answer: A) Task Scheduler
The built-in Task Scheduler is perfect for automating programs to update applications, perform file transfer, or perform
after-hour disk management functions.
Professor Messer’s CompTIA A+ Pop Quiz Sample Archive 10-200
http://ProfessorMesser.com © 2010 Messer Studios, LLC Page 3 of 4
Question 10-203
You’ve been watching your hardware monitoring software, and you’ve noticed that the temperature of your CPU has
increased dramatically in the last few weeks. What’s the most likely cause of the issue?
A) Your computing cycles have increased over the last few weeks
B) The temperature sensor inside of your computer is faulty
C) The fan on your computer isn’t able to pull cool air through the computer
D) The CPU in your computer is failing
E) A small family of guinea pigs has taken a home on your Northbridge
The answer: C) The fan on your computer isn’t able to pull cool air through the computer
Most thermal issues that occur in a computer are due to a decrease of cool air pulled through the computer. This is
usually resolved by cleaning fans, replacing fans, or cleaning dust from the inside and outside of your system.
Question 10-204
You need to increase the storage in a new laptop with an external hard drive, but your applications require high-speed
access to storage. Which of these external hard drive interfaces provide the fastest throughput?
A) SCSI
B) USB
C) FireWire 400
D) eSATA
E) Barbed wire
The answer: D) eSATA
External SATA drive connections provide the same fast throughput as SATA, with SATA II speeds at 300 megabytes per
second.
Professor Messer’s CompTIA A+ Pop Quiz Sample Archive 10-200
http://ProfessorMesser.com © 2010 Messer Studios, LLC Page 4 of 4
Question 10-205
You’re having a problem that you think is related to power. You’re not sure if the problem is related to the voltage from
the wall receptacle or if it’s an issue with your computer’s power supply. What tool would help you troubleshoot this
issue?
A) Multimeter
B) Circuit tester
C) LiveCD
D) UPS
E) Monkey wrench, or perhaps a real monkey
The answer: A) Multimeter
A multimeter is a great tool whenever you have a question about power, wiring, or continuity.
Question 10-208
You’ve plugged in some headphones to your new computer, but you aren’t able to hear any sounds. You’ve checked the
driver settings in your Control Panel and the mixer settings, but all of the settings appear to be configured properly and
set to normal levels. What is the most likely reason for this audio issue?
A) The headphones are plugged into the incorrect jack
B) The headphones are not compatible with the computer audio system
C) The headphones are analog and the computer audio is digital
D) The audio adapter in the computer requires an upgrade to support headphones
E) The headphones disapprove of your taste in music
The answer: A) The headphones are plugged into the incorrect jack
3.5mm headphone jacks look remarkably similar to microphone jacks and line-in jacks. If you aren’t getting any audio,
make sure you’ve connected your headphones to the correct jack!
For futher information, more questions and answers, please do visit
www.sqlauthority.com
C# Interview Questions and Answers
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
C# Interview Questions and Answers
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
C# Interview Questions and Answers
What's C# ?
C# (pronounced C-sharp) is a new object oriented language from Microsoft and is derived from C and C++. It also borrows a lot of concepts from Java too including garbage collection.
Is it possible to inline assembly or IL in C# code?
- No.
Is it possible to have different access modifiers on the get/set methods of a property?
- No. The access modifier on a property applies to both its get and set accessors. What you need to do if you want them to be different is make the property read-only (by only providing a get accessor) and create a private/internal set method that is separate from the property.
Is it possible to have a static indexer in C#? allowed in C#.
- No. Static indexers are not
If I return out of a try/finally in C#, does the code in the finally-clause run?
-Yes. The code in the finally always runs. If you return out of the try block, or even if you do a goto out of the try, the finally block always runs:
using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine(\"In Try block\");
return;
}
finally
{
Console.WriteLine(\"In Finally block\");
}
}
}
Both In Try block and In Finally block will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it’s a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there’s an extra store/load of the value of the expression (since it has to be computed within the try block).
I was trying to use an out int parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as ‘out’, like the following: int i; foo(out i); where foo is declared as follows:
[return-type] foo(out int o) { }
How does one compare strings in C#?
In the past, you had to call .ToString() on the strings when using the == or != operators to compare the strings’ values. That will still work, but the C# compiler now automatically compares the values instead of the references when the == or != operators are used on string types. If you actually do want to compare references, it can be done as follows: if ((object) str1 == (object) str2) { } Here’s an example showing how string compares work:
using System;
public class StringTest
{
public static void Main(string[] args)
{
Object nullObj = null; Object realObj = new StringTest();
int i = 10;
Console.WriteLine(\"Null Object is [\" + nullObj + \"]\n\"
+ \"Real Object is [\" + realObj + \"]\n\"
+ \"i is [\" + i + \"]\n\");
// Show string equality operators
string str1 = \"foo\";
string str2 = \"bar\";
string str3 = \"bar\";
Console.WriteLine(\"{0} == {1} ? {2}\", str1, str2, str1 == str2 );
Console.WriteLine(\"{0} == {1} ? {2}\", str2, str3, str2 == str3 );
}
}
Output:
Null Object is []
Real Object is [StringTest]
i is [10]
foo == bar ? False
bar == bar ? True
How do you specify a custom attribute for the entire assembly (rather than for a class)?
Global attributes must appear after any top-level using clauses and before the first type or namespace declarations. An example of this is as follows:
using System;
[assembly : MyAttributeClass] class X {}
Note that in an IDE-created project, by convention, these attributes are placed in AssemblyInfo.cs.
How do you mark a method obsolete?
[Obsolete] public int Foo() {...}
or
[Obsolete(\"This is a message describing why this method is obsolete\")] public int Foo() {...}
Note: The O in Obsolete is always capitalized.
How do you implement thread synchronization (Object.Wait, Notify,and CriticalSection) in C#?
You want the lock statement, which is the same as Monitor Enter/Exit:
lock(obj) { // code }
translates to
try {
CriticalSection.Enter(obj);
// code
}
finally
{
CriticalSection.Exit(obj);
}
How do you directly call a native function exported from a DLL?
Here’s a quick example of the DllImport attribute in action:
using System.Runtime.InteropServices; \
class C
{
[DllImport(\"user32.dll\")]
public static extern int MessageBoxA(int h, string m, string c, int type);
public static int Main()
{
return MessageBoxA(0, \"Hello World!\", \"Caption\", 0);
}
}
This example shows the minimum requirements for declaring a C# method that is implemented in a native DLL. The method C.MessageBoxA() is declared with the static and external modifiers, and has the DllImport attribute, which tells the compiler that the implementation comes from the user32.dll, using the default name of MessageBoxA. For more information, look at the Platform Invoke tutorial in the documentation.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
What do you know about .NET assemblies?
Assemblies are the smallest units of versioning and deployment in the .NET application. Assemblies are also the building blocks for programs such as Web services, Windows services, serviced components, and .NET remoting applications.
What’s the difference between private and shared assembly?
Private assembly is used inside an application only and does not have to be identified by a strong name. Shared assembly can be used by multiple applications and has to have a strong name.
What’s a strong name?
A strong name includes the name of the assembly, version number, culture identity, and a public key token.
How can you tell the application to look for assemblies at the locations other than its own install?
Use the directive in the XML .config file for a given application.
< probing privatePath=c:\mylibs; bin\debug />
should do the trick. Or you can add additional search paths in the Properties box of the deployed application.
How can you debug failed assembly binds?
Use the Assembly Binding Log Viewer (fuslogvw.exe) to find out the paths searched.
Where are shared assemblies stored?
Global assembly cache.
How can you create a strong name for a .NET assembly?
With the help of Strong Name tool (sn.exe).
Where’s global assembly cache located on the system?
Usually C:\winnt\assembly or C:\windows\assembly.
Can you have two files with the same file name in GAC?
Yes, remember that GAC is a very special folder, and while normally you would not be able to place two files with the same name into a Windows folder, GAC differentiates by version number as well, so it’s possible for MyApp.dll and MyApp.dll to co-exist in GAC if the first one is version 1.0.0.0 and the second one is 1.1.0.0.
So let’s say I have an application that uses MyApp.dll assembly, version 1.0.0.0. There is a security bug in that assembly, and I publish the patch, issuing it under name MyApp.dll 1.1.0.0. How do I tell the client applications that are already installed to start using this new MyApp.dll?
Use publisher policy. To configure a publisher policy, use the publisher policy configuration file, which uses a format similar app .config file. But unlike the app .config file, a publisher policy file needs to be compiled into an assembly and placed in the GAC.
What is delay signing?
Delay signing allows you to place a shared assembly in the GAC by signing the assembly with just the public key. This allows the assembly to be signed with the private key at a later stage, when the development process is complete and the component or assembly is ready to be deployed. This process enables developers to work with shared assemblies as if they were strongly named, and it secures the private key of the signature from being accessed at different stages of development.
Is there an equivalent of exit() for quitting a C# .NET application?
Yes, you can use System.Environment.Exit(int exitCode) to exit the application or Application.Exit() if it's a Windows Forms app.
Can you prevent your class from being inherited and becoming a base class for some other classes?
Yes, that is what keyword sealed in the class definition is for. The developer trying to derive from your class will get a message: cannot inherit from Sealed class WhateverBaseClassName. It is the same concept as final class in Java.
Is XML case-sensitive?
Yes, so and are different elements.
If a base class has a bunch of overloaded constructors, and an inherited class has another bunch of overloaded constructors, can you enforce a call from an inherited constructor to an arbitrary base constructor?
Yes, just place a colon, and then keyword base (parameter list to invoke the appropriate constructor) in the overloaded constructor definition inside the inherited class.
I was trying to use an "out int" parameter in one of my functions. How should I declare the variable that I am passing to it?
You should declare the variable as an int, but when you pass it in you must specify it as 'out', like the following:
int i;
foo(out i);
where foo is declared as follows:
[return-type] foo(out int o) { }
How do I make a DLL in C#?
You need to use the /target:library compiler option.
How do I simulate optional parameters to COM calls?
You must use the Missing class and pass Missing.Value (in System.Reflection) for any values that have optional parameters.
Will finally block get executed if the exception had not occurred?
Yes.
What is the C# equivalent of C++ catch (…), which was a catch-all statement for any possible exception? Does C# support try-catch-finally blocks?
Yes. Try-catch-finally blocks are supported by the C# compiler. Here's an example of a try-catch-finally block: using System;
public class TryTest
{
static void Main()
{
try
{
Console.WriteLine("In Try block");
throw new ArgumentException();
}
catch(ArgumentException n1)
{
Console.WriteLine("Catch Block");
}
finally
{
Console.WriteLine("Finally Block");
}
}
}
Output: In Try Block
Catch Block
Finally Block
If I return out of a try/finally in C#, does the code in the finally-clause run? Yes. The code in the finally always runs. If you return out of the try block, or even if you do a "goto" out of the try, the finally block always runs, as shown in the following
example: using System;
class main
{
public static void Main()
{
try
{
Console.WriteLine("In Try block");
return;
}
finally
{
Console.WriteLine("In Finally block");
}
}
}
Both "In Try block" and "In Finally block" will be displayed. Whether the return is in the try block or after the try-finally block, performance is not affected either way. The compiler treats it as if the return were outside the try block anyway. If it's a return without an expression (as it is above), the IL emitted is identical whether the return is inside or outside of the try. If the return has an expression, there's an extra store/load of the value of the expression (since it has to be computed within the try block).
Is there regular expression (regex) support available to C# developers?
Yes. The .NET class libraries provide support for regular expressions. Look at the documentation for the System.Text.RegularExpressions namespace.
Is there a way to force garbage collection?
Yes. Set all references to null and then call System.GC.Collect(). If you need to have some objects destructed, and System.GC.Collect() doesn't seem to be doing it for you, you can force finalizers to be run by setting all the references to the object to null and then calling System.GC.RunFinalizers().
Does C# support properties of array types?
Yes. Here's a simple example: using System;
class Class1
{
private string[] MyField;
public string[] MyProperty
{
get { return MyField; }
set { MyField = value; }
}
}
class MainClass
{
public static int Main(string[] args)
{
Class1 c = new Class1();
string[] arr = new string[] {"apple", "banana"};
c.MyProperty = arr;
Console.WriteLine(c.MyProperty[0]); // "apple"
return 0;
}
}
What connections does Microsoft SQL Server support?
Windows Authentication (via Active Directory) and SQL Server authentication (via Microsoft SQL Server username and passwords)
What is a satellite assembly?
When you write a multilingual or multi-cultural application in .NET, and want to distribute the core application separately from the localized modules, the localized assemblies that modify the core application are called satellite assemblies.
How is method overriding different from overloading?
When overriding, you change the method behavior for a derived class. Overloading simply involves having a method with the same name within the class.
When do you absolutely have to declare a class as abstract (as opposed to free-willed educated choice or decision based on UML diagram)?
When at least one of the methods in the class is abstract. When the class itself is inherited from an abstract class, but not all base abstract methods have been over-ridden.
Why would you use untrusted verification?
Web Services might use it, as well as non-Windows applications.
What is the implicit name of the parameter that gets passed into the class set method?
Value, and its datatype depends on whatever variable we are changing.
How do I register my code for use by classic COM clients?
Use the regasm.exe utility to generate a type library (if needed) and the necessary entries in the Windows Registry to make a class available to classic COM clients. Once a class is registered in the Windows Registry with regasm.exe, a COM client can use the class as though it were a COM class.
How do I do implement a trace and assert?
Use a conditional attribute on the method, as shown below:
class Debug
{
[conditional("TRACE")]
public void Trace(string s)
{
Console.WriteLine(s);
}
}
class MyClass
{
public static void Main()
{
Debug.Trace("hello");
}
}
In this example, the call to Debug.Trace() is made only if the preprocessor symbol TRACE is defined at the call site. You can define preprocessor symbols on the command line by using the /D switch. The restriction on conditional methods is that they must have void return type.
How do I create a multi language, multi file assembly?
Unfortunately, this is currently not supported in the IDE. To do this from the command line, you must compile your projects into netmodules (/target:module on the C# compiler), and then use the command line tool al.exe (alink) to link these netmodules together.
C# provides a default constructor for me. I write a constructor that takes a string as a parameter, but want to keep the no parameter one. How many constructors should I write?
Two. Once you write at least one constructor, C# cancels the freebie constructor, and now you have to write one yourself, even if there is no implementation in
What is the equivalent to regsvr32 and regsvr32 /u a file in .NET development?
Try using RegAsm.exe. The general syntax would be: RegAsm. A good description of RegAsm and its associated switches is located in the .NET SDK docs. Just search on "Assembly Registration Tool".Explain ACID rule of thumb for transactions.
Transaction must be Atomic (it is one unit of work and does not dependent on previous and following transactions), Consistent (data is either committed or roll back, no in-between case where something has been updated and something hasnot), Isolated (no transaction sees the intermediate results of the current transaction), Durable (the values persist if the data had been committed even if the system crashes right after).
Where is the output of TextWriterTraceListener redirected?
To the Console or a text file depending on the parameter passed to the constructor.
How do I create a multilanguage, single-file assembly?
This is currently not supported by Visual Studio .NET.
Why cannot you specify the accessibility modifier for methods inside the interface?
They all must be public. Therefore, to prevent you from getting the false impression that you have any freedom of choice, you are not allowed to specify any accessibility, it is public by default.
Is it possible to restrict the scope of a field/method of a class to the classes in the same namespace?
There is no way to restrict to a namespace. Namespaces are never units of protection. But if you're using assemblies, you can use the 'internal' access modifier to restrict access to only within the assembly.
Why do I get a syntax error when trying to declare a variable called checked?
The word checked is a keyword in C#.
Why are there five tracing levels in System.Diagnostics.TraceSwitcher?
The tracing dumps can be quite verbose and for some applications that are constantly running you run the risk of overloading the machine and the hard drive there. Five levels range from None to Verbose, allowing to fine-tune the tracing activities.
What is the syntax for calling an overloaded constructor within a constructor (this() and constructorname() does not compile)?
The syntax for calling another constructor is as follows:
class B
{
B(int i)
{ }
}
class C : B
{
C() : base(5) // call base constructor B(5)
{ }
C(int i) : this() // call C()
{ }
public static void Main() {}
}
Why do I get a "CS5001: does not have an entry point defined" error when compiling?
The most common problem is that you used a lowercase 'm' when defining the Main method. The correct way to implement the entry point is as follows:
class test
{
static void Main(string[] args) {}
}
What does the keyword virtual mean in the method definition?
The method can be over-ridden.
What optimizations does the C# compiler perform when you use the /optimize+ compiler option?
The following is a response from a developer on the C# compiler team:
We get rid of unused locals (i.e., locals that are never read, even if assigned).
We get rid of unreachable code.
We get rid of try-catch w/ an empty try.
We get rid of try-finally w/ an empty try (convert to normal code...).
We get rid of try-finally w/ an empty finally (convert to normal code...).
We optimize branches over branches:
gotoif A, lab1
goto lab2:
lab1:
turns into: gotoif !A, lab2
lab1:
We optimize branches to ret, branches to next instruction, and branches to branches.
http://www.aired.in/2009/11/c-sharp-interview-questions-answers.html Or http://www.authorcode.com/c-sharp-interview-questions-and-answers/ Or http://www.careerride.com/CSharp-Interview-Questions.aspx Or http://www.globalguideline.com/interview_questions/Questions.php?sc=C_Sharp_Programming_Language_Interview_Questions_A
CompTIA A+
Pop Quiz Archive
Questions and Answers
SAMPLE
This is a sample archive of the daily CompTIA A+ daily pop quiz that is hosted on http://www.rejictschools.blogsot.com Each
weekday, we send a pop-quiz question to our user community to help them prepare for their CompTIA A+ certification
exam. We hope this compilation will provide you with the information you’ll need to get CompTIA A+ certified.
Our entire library of free CompTIA A+ videos can always be found at http://www.FreeAPlus.com. If you like this taste of
our archive, then you’ll love the entire set. Learn more about our downloadable pop quiz archive athttp://www.rejictschools.blogsot.com
You’d like to use the command line to connect to a Windows share on your central file server. Which command can be
used at a command prompt to connect to a network share?
A) NET CONNECT
B) SHARE USE
C) SHARE CONNECT
D) NET USE
E) O HAI CONNECT THE SHARE PLZ
The answer: D) NET USE
The NET USE command can be used at the command line to connect to a share.
Question 10-202
You need to automate file transfer to occur every morning at 3am. What Windows utility would be a good choice to use
for this requirement?
A) Task Scheduler
B) Task Manager
C) Program Manager
D) Windows Calendar
E) Coffee Maker
The answer: A) Task Scheduler
The built-in Task Scheduler is perfect for automating programs to update applications, perform file transfer, or perform
after-hour disk management functions.
Professor Messer’s CompTIA A+ Pop Quiz Sample Archive 10-200
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Question 10-203
You’ve been watching your hardware monitoring software, and you’ve noticed that the temperature of your CPU has
increased dramatically in the last few weeks. What’s the most likely cause of the issue?
A) Your computing cycles have increased over the last few weeks
B) The temperature sensor inside of your computer is faulty
C) The fan on your computer isn’t able to pull cool air through the computer
D) The CPU in your computer is failing
E) A small family of guinea pigs has taken a home on your Northbridge
The answer: C) The fan on your computer isn’t able to pull cool air through the computer
Most thermal issues that occur in a computer are due to a decrease of cool air pulled through the computer. This is
usually resolved by cleaning fans, replacing fans, or cleaning dust from the inside and outside of your system.
Question 10-204
You need to increase the storage in a new laptop with an external hard drive, but your applications require high-speed
access to storage. Which of these external hard drive interfaces provide the fastest throughput?
A) SCSI
B) USB
C) FireWire 400
D) eSATA
E) Barbed wire
The answer: D) eSATA
External SATA drive connections provide the same fast throughput as SATA, with SATA II speeds at 300 megabytes per
second.
Professor Messer’s CompTIA A+ Pop Quiz Sample Archive 10-200
http://ProfessorMesser.com © 2010 Messer Studios, LLC Page 4 of 4
Question 10-205
You’re having a problem that you think is related to power. You’re not sure if the problem is related to the voltage from
the wall receptacle or if it’s an issue with your computer’s power supply. What tool would help you troubleshoot this
issue?
A) Multimeter
B) Circuit tester
C) LiveCD
D) UPS
E) Monkey wrench, or perhaps a real monkey
The answer: A) Multimeter
A multimeter is a great tool whenever you have a question about power, wiring, or continuity.
Question 10-208
You’ve plugged in some headphones to your new computer, but you aren’t able to hear any sounds. You’ve checked the
driver settings in your Control Panel and the mixer settings, but all of the settings appear to be configured properly and
set to normal levels. What is the most likely reason for this audio issue?
A) The headphones are plugged into the incorrect jack
B) The headphones are not compatible with the computer audio system
C) The headphones are analog and the computer audio is digital
D) The audio adapter in the computer requires an upgrade to support headphones
E) The headphones disapprove of your taste in music
The answer: A) The headphones are plugged into the incorrect jack
3.5mm headphone jacks look remarkably similar to microphone jacks and line-in jacks. If you aren’t getting any audio,
make sure you’ve connected your headphones to the correct jack!
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