top 50 qas in c sharp

8/12/2019 top 50 qas in c sharp

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1. What is C#?

C# is an object oriented, type safe and managed language that is compiled by .Net framework to generate Microsoft Intermediate

Language.

2. What are the types of comment in C#with examples?

Single line

Eg:

[csharp] //This is a Single line comment[/csharp]

ii. Multiple line (/* */)

Eg:

[csharp] /*This is a multiple line comment

We are in line 2Last line of comment*/[/csharp]iii. XML Comments (///).

Eg:

[csharp]/// summary;

/// Set error message for multilingual language.

/// summary[/csharp]

3. Can multiple catch blocks be executed?

No, Multiple catch blocks cant be executed. Once the proper catch code executed, the control is transferred to the finally block

and then the code that follows the finally block gets executed.

4. What is the difference between public, static and void?

All these are access modifiers in C#. Public declared variables or methods are accessible anywhere in the application. Static

declared variables or methods are globally accessible 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. And Void is a type

modifier that states that the method or variable does not return any value.

5. What is an object?

An object is an instance of a class through which we access the methods of that class. New keyword is used to create an obj ect.

A class that creates an object in memory will contain the information about the methods, variables and behavior of that class.

6. Define Constructors?

A constructor is a member function in a class that has the same name as its class. The constructor is automatically invoked

whenever an object class is created. It constructs the values of data members while initializing the class.

7. What is Jagged Arrays?

The array which has elements of type array is called jagged array. The elements can be of different dimensions and sizes. We can

also call jagged array as Array of arrays.


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8. What is the difference between ref & out parameters?

An argument passed as ref must be initialized before passing to the method whereas out parameter needs not to be initialized

before passing to a method.

9. What is the use of using statement in C#?

The using block is used to obtain a resource and use it and then automatically dispose of when the execution of block completed.

10. What is serialization?

When we want to transport an object through network then we have to convert the object into a stream of bytes. The process of

converting an object into a stream of bytes is called Serialization. For an object to be serializable, it should inherit ISerialize

Interface.

De-serialization is the reverse process of creating an object from a stream of bytes.

11. Can this be used within a static method?

We cant use This in a static method because we can only use static variables/methods in a static method.

12. What is difference between constants and read-only?

Constant variables are declared and initialized at compile time. The value cant be changed after wards. Read-only variables will

be initialized only from the Static constructor of the class. Read only is used only when we want to assign the value at run time.

13. What is aninterface class?

Interface is an abstract class which has only public abstract methods and the methods only have the declaration and not thedefinition. These abstract methods must be implemented in the inherited classes.

14. What are value types and reference types?

Value types are stored in the Stack whereas reference types stored on heap.

Value types:

[csharp] int, enum , byte, decimal, double, float, long[/csharp]

Reference Types:

[csharp] string , class, interface, object.[/csharp]

15. What are Custom Control and User Control?

Custom Controls are controls generated as compiled code (Dlls), those are easier to use and can be added to toolbox. Developers

can drag and drop controls to their web forms. Attributes can be set at design time. We can easily add custom controls to Multiple

Applications (If Shared Dlls), If they are private then we can copy to dll to bin directory of web application and then add

reference and can use them.

User Controls are very much similar to ASP include files, and are easy to create. User controls cant be placed in the toolbox and


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draggeddropped from it. They have their design and code behind. The file extension for user controls is ascx.

16. What are sealed classes in C#?

We create sealed classes when we want to restrict the class to be inherited. Sealed modifier used to prevent derivation from a

class. If we forcefully specify a sealed class as base class then a compile-time error occurs.

17. What ismethod overloading?

Method overloading is creating multiple methods with the same name with unique signatures in the same class. When we

compile, the compiler uses overload resolution to determine the specific method to be invoke.

18. What is the difference between Array and Arraylist?

In an array, we can have items of the same type only. The size of the array is fixed. An arraylist is similar to an array but it

doesnt have a fixed size.

19. Can a private virtual method be overridden?

No, because they are not accessible outside the class.

20. Describe the accessibility modifier protected internal.

Protected Internal variables/methods are accessible within the same assembly and also from the classes that are derived from this

parent class.

21. What are the differences between System.String and System.Text.StringBuilder classes?

System.String is immutable. When we modify the value of a string variable then a new memory is allocated to the new value andthe previous memory allocation released. System.StringBuilder was designed to have concept of a mutable string where a variety

of operations can be performed without allocation separate memory location for the modified string.

22. Whats the difference between the System.Array.CopyTo() and System.Array.Clone() ?

Using Clone() method, we creates a new array object containing all the elements in the original array and using CopyTo()

method, all the elements of existing array copies into another existing array. Both the methods perform a shallow copy.

23. How can we sort the elements of the array in descending order?

Using Sort() methods followed by Reverse() method.

24. Write down the C# syntax to catch exception?

To catch an exception, we use try catch blocks. Catch block can have parameter of system.Exception type.

Eg:

[csharp]try

{


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GetAllData();

}

catch(Exception ex)

{

}[/csharp]

In the above example, we can omit the parameter from catch statement.

25. Whats the difference between aninterface and abstract class?

Interfaces have all the methods having only declaration but no definition. In an abstract class, we can have some concrete

methods. In an interface class, all the methods are public. An abstract class may have private methods.

26. What is the difference betweenFinalize() and Dispose() methods?

Dispose() is called when we want for an object to release any unmanaged resources with them. On the other hand Finalize() is

used for the same purpose but it doesnt assure the garbage collection of an object.

27. What are circular references?

Circular reference is situation in which two or more resources are interdependent on each other causes the lock condition and

make the resources unusable.

28. What are generics in C#.NET?

Generics are used to make reusable code classes to decrease the code redundancy, increase type safety and performance. Using

generics, we can create collection classes. To create generic collection, System.Collections.Generic namespace should be used

instead of classes such as ArrayList in the System.Collections namespace. Generics promotes the usage of parameterized types.

29. What is an object pool in .NET?

An object pool is a container having objects ready to be used. It tracks the object that is currently in use, total number of objects

in the pool. This reduces the overhead of creating and re-creating objects.

30. List down the commonly used types of exceptions in .Net?

ArgumentException, ArgumentNullException , ArgumentOutOfRangeException, ArithmeticException, DivideByZeroException

,OverflowException , IndexOutOfRangeException ,InvalidCastException ,InvalidOperationException ,

IOEndOfStreamException , NullReferenceException , OutOfMemoryException , StackOverflowException etc.

31. What are Custom Exceptions?

Sometimes there are some errors that need to be handeled as per user requirements. Custom exceptions are used for them and are

used defined exceptions.

32. What are delegates?

Delegates are same are function pointers in C++ but the only difference is that they are type safe unlike function pointers.

Delegates are required because they can be used to write much more generic type safe functions.


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33. How do you inherit a class into other class in C#?

Colon is used as inheritance operator in C#. Just place a colon and then the class name.

[csharp] public class DerivedClass : BaseClass[/csharp]

34. What is the base class in .net from which all the classes are derived from?

[csharp]System.Object[/csharp]

35. What is the difference between method overriding and method overloading?

In method overriding, we change the method definition in the derived class that changes the method behavior. Method

overloading is creating a method with the same name within the same class having different signatures.

36. What are the different ways a method can be overloaded?

Methods can be overloaded using different data types for parameter, different order of parameters, and different number of

parameters.

37. Why cant you specify the accessibility modifier for methods inside the interface?

In an interface, we have virtual methods that do not have method definition. All the methods are there to be overridden in the

derived class. Thats why they all are public.

38. How can we set class to be inherited, but prevent the method from being over-ridden?

Declare the class as public and make the method sealed to prevent it from being overridden.

39. What happens if the inherited interfaces have conflicting method names?

Implement is up to you as the method is inside your own class. There might be problem when the methods from different

interfaces expect different data, but as far as compiler cares youre okay.

40. What is the difference between a Struct and a Class?

Structs are value-type variables and classes are reference types. Structs stored on the stack, causes additional overhead but faster

retrieval. Structs cannot be inherited.

41. How to use nullable types in .Net?

Value types can take either their normal values or a null value. Such types are called nullable types.

[csharp]Int? someID = null;If(someID.HasVAlue)

{

}

[/csharp]


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42. How we can create an array with non-default values?

We can create an array with non-default values using Enumerable.Repeat.43. What is difference between is and as operators in c#?

is operator is used to check the compatibility of an object with a given type and it returns the result as Boolean.

as operator is used for casting of object to a type or a class.

44. Whats a multicast delegate?

A delegate having multiple handlers assigned to it is called multicast delegate. Each handler is assigned to a method.

45. What are indexers in C# .NET?

Indexers are known as smart arrays in C#. It allows the instances of a class to be indexed in the same way as array.

Eg:

[csharp]public int this[int index] // Indexer declaration[/csharp]

46. What is difference between the throw and throw ex in .NET?

Throw statement preserves original error stack whereas throw ex have the stack trace from their throw point. It is always

advised to use throw because it provides more accurate error information.

47. What are C# attributes and its significance?

C# provides developers a way to define declarative tags on certain entities eg. Class, method etc. are called attributes. Theattributes information can be retrieved at runtime using Reflection.

48. How to implement singleton design pattern in C#?

In singleton pattern, a class can only have one instance and provides access point to it globally.

Eg:

[csharp]

Public sealed class Singleton

{

Private static readonly Singleton _instance = new Singleton();

}

[/csharp]

49. What is the difference between directcast and ctype?

DirectCast is used to convert the type of an object that requires the run-time type to be the same as the specified type in

DirectCast.

Ctype is used for conversion where the conversion is defined between the expression and the type.

50. Is C# code is managed or unmanaged code?

C# is managed code because Common language runtime can compile C# code to Intermediate language.


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125 Basic C# Interview Questions and

Answers125 Basic C# Interview Questions and Answers

Below is the list of 125 basic C# interview questions with their answers. These C# interview questions

and answers are very simple and straight-forward which cover the basic concepts of C# mostly related to

object oriented concepts. So if you are preparing for C# interview, I will suggest you to must go through

these 125 C# basic interview questions and answers to revise your C# concepts. Here goes the list of

125 basic C# interview questions and answers.

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

FlexibleObject oriented

Compatible

Consistent

Interoperable

Modern

5. What are the different categories of inheritance?


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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#?


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Abstract

Sealed

Virtual

Const

EventExtern

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 behaviors (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.


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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 precised 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 accesslevels. 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.


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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 behaviors 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 arrayofarrays.

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-serializationis 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.


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Classes can have both contractors and destructors.

Structures do not support Inheritance, while Classes support Inheritance.

33. What is difference between Class And Interface?

Classis logical representation of object. It is collection of data and related sub procedures with

defination.

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 cant 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#?


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C# supports several different kinds of statements are

Block statements

Declaration statements

Expression statementsSelection 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.


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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 ifPrivate 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#?


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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 sealedclass 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.


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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 doesnthave 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)


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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 toinstances 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 users 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 returnstatement 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?


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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 comlicated 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.


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81. What is the difference between CONST and READONLY?

Both 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 objects 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 doublequote character, such as "hello".


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The Null literal: Represents the nulltype.

88. What is meant by data encapsulation?

Data encapsulation, also referred to as data hiding, is the mechanism whereby the implementation detailsof 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?


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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 inderived classes.

104. What are constructors and destructors?

Constructors and destructors are special methods.

Constructors and destructors are special methods of every class.


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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.


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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.


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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 class and an Interface?

Abstract classes can have implementations for some of its members, but the interface can't have

implementation for any of its members.

Interfaces cannot have fields where as an abstract class can have fields.

An interface can inherit from another interface only and cannot inherit from an abstract class, where as an

abstract class can inherit from another abstract class or another interface.

A class can inherit from multiple interfaces at the same time, where as a class cannot inherit from multiple

classes at the same time.

Abstract class members can have access modifiers where as interface members cannot have access

modifiers.

121. What is the difference between an abstract method & virtual method?

An Abstract method does not provide an implementation and forces overriding to the deriving class

(unless the deriving class also an abstract class), where as the virtual method has an implementation and

leaves an option to override it in the deriving class. Thus Virtual method has an implementation &

provides the derived class with the option of overriding it. Abstract method does not provide

an implementation & forces the derived class to override the method.

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.


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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 atdeclaration 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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