C#.NET Interview QA

C#.NET

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. What is scope?

Scope refers to the region of code in which a variable may be accessed.

10. 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. 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 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.

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 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 behaviors in different instances.