1. What
is C#?
C# (pronounced "C sharp") is a
simple, modern, object-oriented, and type-safe programming language.
It will immediately be
familiar to C and C++ programmers.
C# combines the high productivity of Rapid Application Development (RAD) languages.
2. What
are the types of comment in C#?
There are 3 types of comments in C#.
Single line (//)
Multi (/* */)
Page/XML Comments (///).
3. What
are the namespaces used in C#.NET?
Namespace is a logical grouping of
class.
using System;
using System.Collections.Generic;
using System.Windows.Forms;
4. What
are the characteristics of C#?
There are several characteristics of
C# are :
Simple
Type safe
Flexible
Object oriented
Compatible
Consistent
Interoperable
Modern
5. What
are the different categories of inheritance?
Inheritance
in Object Oriented Programming is of four types:
Single inheritance : Contains one base class
and one derived class.
Hierarchical inheritance : Contains one base class
and multiple derived classes of the same base class.
Multilevel inheritance : Contains a
class derived from a derived class.
Multiple inheritance : Contains several
base classes and a derived class.
6. What
are the basic concepts of object oriented programming?
It is necessary to understand some of the concepts
used extensively in object oriented programming.These include
Objects
Classes
Data abstraction and encapsulation
Inheritance
Polymorphism
Dynamic Binding
Message passing.
7. Can
you inherit multiple interfaces?
Yes. Multiple
interfaces may be inherited in C#.
8. What
is inheritance?
Inheritance is deriving the new class
from the already existing one.
9. Define
scope?
Scope refers to the region of code in which a variable
may be accessed.
10. What
is the difference between public, static and void?
public :The keyword public is an access modifier
that tells the C# compiler that the Main method is accessible by anyone.
static :The keyword static declares that the Main
method is a global one and can be called without creating an instance
of the class. The compiler stores the address of the method as the entry point and
uses this information to begin execution before any objects are created.
void : The keyword void is a type modifier
that states that the Main method does not return any value.
11. What
are the modifiers in C#?
Abstract
Sealed
Virtual
Const
Event
Extern
Override
Readonly
Static
New
12. What
are the types of access modifiers in C#?
Access modifiers in C# are :
public
protect
private
internal
internal protect
13. What
is boxing and unboxing?
Implicit conversion of value type to reference type of a variable is known as BOXING, for example integer to
object type conversion.
Conversion
of reference
type variable back to value type is called as UnBoxing.
14. What
is object?
An object is an instance of a class. An
object is created by using operator new. A class that creates an object in
memory will contain the information about the values and behaviours (or methods)
of that specific object.
15. Where
are the types of arrays in C#?
Single-Dimensional
Multidimensional
Jagged arrays.
16. What
is the difference between Object and Instance?
An instance of a user-defined type is
called an object. We can instantiate many objects from one class.
An
object is an instance of a class.
17. Define
destructors?
A destructor is called for a class object when that
object passes out of scope or is explicitly deleted.A destructors as the
name implies is used to destroy the objects that have been created by a constructors.Like
a constructor , the destructor is a member function whose name is the same
as the class name but is precided by a tilde.
18. What
is the use of enumerated data type?
An enumerated data type is another user defined
type which provides a way for attaching names to numbers thereby
increasing comprehensibility of the code. The enum keyword
automatically enumerates a list of words by assigning them values 0,1,2, and so
on.
19. Define
Constructors?
A constructor is a member function with the
same name
as its class. The constructor is invoked whenever an
object of its associated class is created.It is called constructor because it constructs
the values of data members of the class.
20. What
is encapsulation?
The wrapping up of data and functions into a single
unit (called class) is known as encapsulation. Encapsulation
containing and hiding information about an object, such as internal data
structures and code.
21. Does
c# support multiple inheritance?
No,its impossible
which accepts multi level inheritance.
22. What
is ENUM?
Enum are used to define constants.
23. What
is a data set?
A DataSet is an in memory representation of
data loaded from any data source.
24. What
is the difference between private and public keyword?
Private : The private keyword is the default access
level and most restrictive among all other access levels. It gives least
permission to a type or type member. A private member is accessible
only within
the body of the class in which it is declared.
Public : The public keyword is most liberal among
all access levels, with no restrictions to access what so ever. A
public member is accessible not only from within, but also from outside, and
gives free access to any member declared within the body or outside the body.
25. Define
polymorphism?
Polymorphism means one name, multiple forms.
It allows us to have more than one function with the same name in a program.It
allows us to have overloading of operators so that an operation can exhibit different
behaviours in different instances.
26. What
is Jagged Arrays?
A jagged array is an array whose elements are
arrays.
The elements of a jagged array can be of
different
dimensions and sizes.
A jagged array is sometimes called an array–of–arrays.
27. what
is an abstract base class?
An abstract class is a class that is designed to be
specifically used as a base class. An abstract class contains at
least one
pure virtual function.
28. How
is method overriding different from method overloading?
When overriding a method, you change the
behavior of the method for the derived class. Overloading a method
simply involves having another method with the same name within the class.
29. What
is the difference between ref & out parameters?
An argument passed to a ref parameter must first be initialized.
Compare this to an out parameter, whose argument does not have to be explicitly
initialized before being passed to an out parameter.
30. What
is the use of using statement in C#?
The using statement is used to obtain a
resource, execute a statement, and then dispose of that resource.
31. What
is serialization?
Serialization is the process of converting an
object into a stream of bytes.
De-serialization
is the opposite process of creating an object from a stream of bytes.
Serialization
/ De-serialization is mostly used to transport objects.
32. What
are the difference between Structure and Class?
Structures are value type and Classes
are reference
type
Structures can not have contractors or
destructors.
Classes can have both
contractors and destructors.
Structures do not support Inheritance,
while Classes
support Inheritance.
33. What
is difference between Class And Interface?
Class : is logical representation of object.
It is collection of data and related sub procedures with definition.
Interface
: is also a class containg methods which is not having any definations.Class
does
not support multiple inheritance. But interface can support.
34. What
is Delegates?
Delegates are a type-safe,
object-oriented implementation of function pointers and are used in
many situations where a component needs to call back to the component that is
using it.
35. What
is Authentication and Authorization?
Authentication is the process of identifying
users. Authentication is identifying/validating the user against the credentials
(username and password).
Authorization
performs after authentication. Authorization is the process of granting access
to those users based on identity. Authorization allowing access of specific
resource to user.
36. What
is a base class?
A class declaration may specify a base
class by following the class name with a colon and the name of the base class.
Omitting a base class specification is the same as deriving from type object.
37. Can
“this” be used within a static method?
No ‘This’ cannot be used in a static method.
As only static variables/methods can be used in a static method.
38. What
is difference between constants, readonly and, static ?
Constants: The value can’t be
changed.
Read-only: The value will be initialized
only once from the constructor of the class.
Static: Value can be initialized
once.
39. What
are the different types of statements supported in C#?
C# supports several different kinds of
statements are
Block statements
Declaration statements
Expression statements
Selection statements
Iteration statements
Jump statements
Try catch statements
Checked and unchecked
Lock statement
40. What
is an interface class?
It is an abstract class with public
abstract methods all of which must be implemented in the inherited classes.
41. what
are value types and reference types?
Value types are stored in the Stack.
Examples
: bool, byte, chat, decimal, double, enum , float, int, long, sbyte, short,
strut, uint, ulong, ushort.
Reference
types are stored in the Heap.
Examples
: class, delegate, interface, object, string.
42. What
is the difference between string keyword and System.String class?
String keyword is an alias for
Syste.String class. Therefore, System.String and string keyword are
the same, and you can use whichever naming convention you prefer. The String
class provides many methods for safely creating, manipulating, and comparing
strings.
43. What
are the two data types available in C#?
Value type
Reference type
44. What
are the different types of Caching?
There are three types of Caching :
Output Caching: stores the responses
from an asp.net page.
Fragment Caching: Only caches/stores the
portion
of page (User Control)
Data Caching: is Programmatic way to Cache objects
for performance.
45. What
is the difference between Custom Control and User Control?
Custom Controls are compiled code (Dlls),
easier
to use, difficult to create, and can be placed in toolbox. Drag and
Drop controls. Attributes can be set visually at design time. Can be used by
Multiple Applications (If Shared Dlls), Even if Private can copy to bin
directory of web application add reference and use. Normally designed to provide common
functionality independent of consuming Application.
User
Controls are similar to those of ASP include files, easy to create, can not be
placed in the toolbox and dragged - dropped from it. A User Control is shared
among the single application files.
46. What
is methods?
A method is a member that implements a
computation or action that can be performed by an object or class. Static
methods are accessed through the class. Instance methods are accessed
through instances of the class.
47. What
is fields?
A field is a variable that is
associated with a class or with an instance of a class.
48. What
is events?
An event is a member that enables a class or object
to provide notifications. An event is declared like a field except
that the declaration includes an event keyword and the type must be a delegate
type.
49. What
is literals and their types?
Literals are value constants assigned
to variables
in a program. C# supports several types of literals are
Integer literals
Real literals
Boolean literals
Single character literals
String literals
Backslash character literals
50. What
is the difference between value type and reference type?
Value types are stored on the stack
and when a value of a variable is assigned to another variable.
Reference types are stored on the heap,
and when an assignment between two reference variables occurs.
51. What
are the features of c#?
C# is a simple and powerful programming
language for writing enterprise edition applications.
This is a hybrid of C++ and VB.
It retains many C++ features in the area statements,expressions, and operators
and incorporated the productivity of VB.
C# helps the developers to easily build
the web services that can be used across the Internet through any language, on
any platform.
C# helps the developers accomplishing
with fewer lines of code that will lead to the fewer errors in the code.
C# introduces the considerable
improvement and innovations in areas such as type safety,versioning. events and
garbage collections.
52. What
are the types of errors?
Syntax error
Logic error
Runtime error
53. What
is the difference between break and continue statement?
The break statement is used to terminate
the current enclosing loop or conditional statements in which it
appears. We have already used the break statement to come out of switch
statements.
The
continue statement is used to alter the sequence of execution. Instead
of coming out of the loop like the break statement did, the continue statement
stops the current iteration and simply returns control back to the top of the loop.
54. Define
namespace?
The namespace are known as containers
which will be used to organize the hierarchical set of .Net classes.
55. What
is a code group?
A code group is a set of
assemblies that share a security context.
56. What
are sealed classes in C#?
The sealed modifier is used to prevent
derivation
from a class. A compile-time error occurs if a sealed class is
specified as the base class of another class.
57. What
is the difference between static and instance methods?
A method declared with a static modifier
is a static method. A static method does not operate on a specific
instance and can only access static members.
A
method declared without a static modifier is an instance method. An
instance method operates on a specific instance and can access both static and
instance members. The instance on which an instance method was
invoked can be explicitly accessed as this. It is an error to refer to this in
a static method.
58. What
are the different types of variables in C#?
Different types of variables used in C#
are :
static variables
instance variable
value parameters
reference parameters
array elements
output parameters
local variables
59. What
is meant by method overloading?
Method overloading permits multiple
methods in the same class to have the same name as long as they have
unique signatures. When compiling an invocation of an overloaded method, the
compiler uses overload resolution to determine the specific method to invoke
60. What
is parameters?
Parameters are used to pass values or
variable references to methods. The parameters of a method get their
actual values from the arguments that are specified when the method is
invoked. There are four kinds of parameters: value parameters,
reference parameters, output parameters, and parameter arrays.
61. Is
C# is object oriented?
YEs, C# is an OO langauge
in the tradition of Java and C++.
62. What
is the difference between Array and Arraylist?
An array is a collection of the same type.
The size of the array is fixed in its declaration. A linked list is similar to an
array but it doesn’t have a limited size.
63. What
are the special operators in C#?
C# supports the following special
operators.
is (relational operator)
as (relational operator)
typeof (type operator)
sizeof (size operator)
new (object creator)
.dot (member access operator)
checked (overflow checking)
unchecked (prevention of overflow
checking)
64. What
is meant by operators in c#?
An operator is a member that defines
the meaning
of applying a particular expression operator to instances of a class.
Three kinds of operators can be defined: unary operators, binary operators, and
conversion operators. All operators must be declared as public and
static.
65. What
is a parameterized type?
A parameterized type is a type that is
parameterized
over another value or type.
66. What
are the features of abstract class?
An abstract class cannot be
instantiated, and it is an error to use the new operator on an abstract
class.
An abstract class is permitted (but not
required) to contain abstract methods and accessors.
An abstract class cannot be
scaled.
67. What
is the use of abstract keyword?
The modifier abstract is a keyword
used with
a class, to indicate that this class cannot itself have direct
instances or objects, and it is intended to be only a 'base' class
to other classes.
68. What
is the use of goto statement?
The goto statement is also included in
the C#
language. This goto can be used to jump from inside a loop to outside.
But jumping from outside to inside a loop is not allowed.
69. What
is the difference between console and window application?
A console application, which is designed
to run at the command line with no user interface.
A Windows application, which is designed
to run on a user’s desktop and has a user interface.
70. What
is the use of return statement?
The return statement is associated with procedures
(methods or functions). On executing the return statement, the
system passes the control from the called procedure to the calling procedure.
This return statement is used for two purposes :
to return immediately to the caller
of the currently executed code
to return some value to the caller
of the currently executed code.
71. What
is the difference between Array and LinkedList?
Array is a simple sequence of numbers
which are not concerned about each others positions. they are independent of
each others positions. adding,removing or modifying any array
element is very easy. Compared to arrays ,linked list is a complicated
sequence of numbers.
72. Does
C# have a throws clause?
No, unlike Java, C# does
not require the developer to specify the exceptions that a method can throw.
73. Does
C# support a variable number of arguments?
Yes, uisng the params
keyword. The arguments are specified as a list of arguments of a specific type.
74. Can
you override private virtual methods?
No, private methods are not
accessible outside the class.
75. What
is a multi cast delegates?
Each delegate object holds reference
to a single method. However, it is possible for a delegate object to
hold
references of and invoke multiple methods. Such delegate objects
are called multicast delegates or combinable delegates.
76. Which
is an exclusive feature of C#?
Xml documentation.
77. Is
using of exceptions in C# recommended?
Yes, exceptions are the
recommended error handling mechanism in .NET Framework.
78. What
does a break statement do in switch statements?
The break statement terminates
the loop in which it exists. It also changes the flow of the
execution of a program.
In switch statements, the break
statement is used at the end of a case statement. The break statement is mandatory in C#
and it avoids the fall through of one case statement to another.
79. Is
C# object oriented?
Yes, C# is an OO language
in the tradition of java and C++.
80. What
is smart navigation?
The cursor position is maintained when the page gets
refreshed due to the server side validation and the page gets refreshed.
81. What
is the difference between CONST and READONLY?
sBoth
are meant for constant values. A const field can only be initialized at the declaration of
the field. A readonly field can be initialized either at the
declaration or.
82. Does
C# have a throws clause?
No, unlike Java, C# does
not require (or even allow) the developer to specify the exceptions that a
method can throw.
83. What
are the different ways a method can be overloaded?
Different parameter data types,
different number of parameters, different order of parameters.
84. Do
events have return type?
No, events do not have return
type.
85. What
is event?
An event is an action performed based on another method
of the program.
An event is a delegate type dass member
that is used by an object or a class to provide a notification to other objescts
that an event has occurred.
An event can be declared with the help
of the event keyword.
86. What
is an identifier?
Identifiers are nothing but names
given to various entities uniquely identified in a program.
87. What
are the different types of literals in C#?
Boolean literals : True and False are
literals of the Boolean type that map to the true and false state,
respectively.
Integer literals : Used to write values
of types Int, ulnt, long, and ulong.
Real literals : Used to write values of
types float,
double, and dedmal.
Character literals : Represents a single
character and usually consists of a character in quotes, such as 'a'.
String literals : C# supports two types
of string literals, regular string literal and verbatim string literals.
A regular string literal consists of zero or more characters enclosed in double
quotes, such as "116110". A verbatim string literal
consists of an @ character followed by a double–quote character, such as
©"hello".
The Null literal : Represents the null–type.
88. What
is meant by data encapsulation?
Data encapsulation, also referred to
as data
hiding, is the mechanism whereby the implementation details of a
class are kept hidden from the user. The user can only perform a restricted
set of operations on the hidden members of the class by executing special functions
called methods.
89. Can
you override private virtual methods?
No. Private methods are
not accessible outside the class.
90. What
is the main difference between a subprocedure and a function?
Subprocedures do not return
a value, while functions do.
91. How
does C# differ from C++?
C# does not support #include
statement. It uses only using statement.
In C# , class definition does not use a
semicolon at the end.
C# does not support multiple code
inheritance.
Casting in C# is much
safer than in c++.
In C# switch can also be used on string
values.
Command line parameters array behave
differently in C# as compared to C++.
92. What
is nested class?
A Nested classes are classes within
classes.
A nested class is any class whose
declaration occurs within the body of another class or interface.
93. Can
you have parameters for static constructors?
No, static constructors
cannot have parameters.
94. Is
String is Value Type or Reference Type in C#?
String is an object(Reference
Type).
95. Does
C# provide copy constructor?
No, C# does not provide
copy constructor.
96. Can
a class or a struct have multiple constructors?
Yes, a class or a struct
can have multiple constructors. Constructors in C# can be overloaded.
97. Can
you create an instance of an interface?
No, you cannot create an
instance of an interface.
98. Can
an Interface contain fields?
No, an Interface cannot
contain fields.
99. Can
a class have static constructor?
Yes,
a class can have static constructor. Static constructors are
called automatically, immediately before any static fields are accessed, and
are generally used to initialize static class members. It is called
automatically before the first instance is created or any static members
are referenced. Static constructors are called before instance
constructors. An example is shown below.
100. What
is the main use of delegates in C#?
Delegates are mainly used to define call back
methods.
101. What
is the difference between Shadowing and Overriding?
Overriding redefines only the implementation while
shadowing redefines the whole element.
In overriding derived classes can refer
the parent class element by using "ME" keyword, but in shadowing
you can access it by "MYBASE".
102. Can
events have access modifiers?
Yes, you can have access modifiers in
events. You can have events with the protected keyword, which
will be accessible only to inherited classes. You can have private events
only for objects in that class.
103. Why
is the virtual keyword used in code?
The Virtual keyword is used in code to
define methods and the properties that can be overridden in derived classes.
104. What
are constructors and destructors?
Constructors and destructors are special
methods.
Constructors and destructors are special
methods of every class.
Each class has its own constructor and
destructor and are called automatically when the instance of a class is created or
destroyed.
The constructor initializes all class
members whenever you access the class and the destructor destroys them when the
objects are not required anymore.
105. How
can we suppress a finalize method?
GC.SuppressFinalize()
106. Does
C# support a variable number of arguments?
Yes, using the params keyword.
The arguments are specified as a list of
arguments of a specific type, e.g., int. For ultimate flexibility, the type can
be object.
The standard example of a method which
uses this approach is System.console.writeLine().
107. Which
method will you call to start a thread?
Start
108. What
is Generic?
Generic help us to create flexible strong type
collection.
Generic basically seperate the logic from the
datatype in order maintain better reusability, better
maintainability etc.
109. What
are the different types of polymorphism?
There are two types of polymorphism. They
are
Compile time Polymorphism
Run time Polymorphism
110. What
is the difference between compile time polymorphism and run time polymorphism?
Compile time Polymorphism
Compile time Polymorphism also known as method
overloading.
Method overloading means having two or
more methods with the same name but with different signatures.
Run time Polymorphism
Run time Polymorphism also known as method overriding.
Method overriding means having two or
more methods with the same name , same signature but with different
implementation.
111. Which
namespace enables multithreaded programming in XML?
System.Threading
112. Can
we declare a block as static in c#?
No, because c# doesnot
support static block, but it supports static method.
113. Can
we declare a method as sealed?
In C# a method can't be
declared as sealed. However when we override a method in a derived
class, we can declare the overridden method as sealed. By declaring it as
sealed, we can avoid further overriding of this method.
114. What
Command is used to implement properties in C#?
get & set access modifiers are
used to implement properties in c#.
115. What
is static member?
The member defined as static which can
be invoked directly from the class level, rather than from its instance.
116. What
is the syntax to inherit from a class in C#?
When a class is derived
from another class, then the members of the base class become the members of
the derived class.
The access modifier used while accessing
members of the base class specifies the access status of the base class
members inside the derived class.
The syntax to inherit a class from
another class In C# is as follows :
class
MyNewClass : MyBaseClass
117. What
is a basic difference between the while loop and do while loop in C#?
The while loop tests its condition at
the beginning, which means that the enclosed set of statements run for zero or
more number of times if the condition evaluates to true. The do while loop
iterates a set of statements at least once and then checks the condition at the
end.
118. What
is the main difference between a subprocedure and a function?
Subprocedures do not return a value,
while functions do.
119. What
are sealed classes in c#?
The sealed modifier is used to prevent
derivation from a class.
A compile time error occurs if a sealed class is
specified as the base class of another class.
120. What
is the difference between Abstract class and an Interface?
Abstract class:
1.Abstract class can contain methods
with both
implemetaion and without implementation
2.An
abstract class can implement a property
3.Multiple
inheritance is not possible in case of abstract class
4.Access
Specifiers are been Supported in abstract class
5.An
abstract class can contain constructors or destructors.
6.An
abstract class cannot be inherited from by structures
Interface :
1.Does
not contain any concrete methods
2.An
Interface can contain property definitions.
3.Multiple Inheritance is possible with interface
4.Access Specifiers are not supported in Interface
5.An
Interface cannot contain constructors or destructors
6.An
Interface can be inherited from by structures
121. What
is the difference between an abstract method & virtual method?
An Abstract method must be overriden
in child
classes where as virtual method is not compulsory to override.
An
abstract method doesn't have implementation detail where as virtual method
has it.
only abstract
class can have abstract method, any class can have virtual method
abstract == MustOverride,virtual == Overridable
122. What
is Static Method?
It is possible to declare a method as
Static provided that they don't attempt to access any instance data or other
instance methods.
123. What
is a New modifier?
The new modifier hides a member
of the base class. C# supports only hide by signature.
124. What
are the advantages of get and set properties in C#?
The get property accessor is used to
return the property value.
The set property accessor is used to assign a new
value.
125. What
are the difference between const and readonly?
A const can not be static, while readonly can be
static.
A const need to be declared and
initialized at declaration only, while a readonly can be initialized at
declaration or by the code in the constructor.
A const's value is evaluated at design time,
while a readonly's value is evaluated at runtime.
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