C# interview questions and answers

C# is a modern, high level, general purpose object oriented programming language. This language is principal language of .Net framework. The design goal of the language was software robustness, durability & programmer productivity. It can be used to create a console application, GUI application, web application both on PC or embedded systems.

1. Single line
   //This is a Single line comment
   
   
2. Multiple line
   /*This is a multiple line comment
   Here you can use more than 1 line*/
   
   
3. XML Comments
   /// This is XML code Comment.
   

A class describes all attributes of objects as well as the method that implements the behavior of member object. Basically, it represents a blue print of object. It is a template of an object. A class contains data & behavior of an entity.
Example: Aircraft.
Data: Model number of aircraft, Color of aircraft, category of aircraft etc.
Behavior/Method: Duration of flight, number of passengers etc.

An object is an instance of the class. It is a basic unit of the system. An object is an entity that has attributes, behavior & identity. Attributes & behavior of an object is defined by the class definition.

They both look very much same but they are not same. The class is definition while the object is the instance of the class created. The class is blue print while objects are actual objects existing in the world.
Example: Car has attributes & method like speed, brake, type of car etc.

Following are the advantages of C#

1. Easy to learn
2. Object oriented
3. Component oriented
4. Part of .NET framework

Following are the IDE’s used for C# development

1. Visual Studio Express (VCE)
2. Visual Studio (VS)
3. Visual Web Developer

Struct & Class both are the user defined data type but have some major differences:

1. Both can have a constructor, method/functions, properties, fields, constants, enumeration, events & event handler.
2. Structure & classes can implement the interface.
3. Both of them can have a constructor with & without parameters.
4. Both can have delegates & events.

Oops stands for object oriented programming system. It is a problem-solving technique to think real world problems in terms of objects.

Following are different properties provided by oops

1. Inheritance: It is a process of forming new class from the existing class.
   Example: A scientific calculator is an extended form of a calculator. Here, the calculator is the parent & scientific calculator is child object.
   
   
2. Polymorphism: The ability to use an operator or functions in different ways giving different meaning to function to the operator is called polymorphism.
   Example: A person is behaving like a Child, professor, student and then as a clerk. This is the power of polymorphism, a single object behaves in different forms.
   
   
3. Encapsulation: Encapsulate means to hide also called as data hiding. Encapsulation is used to hide the code & data in a single unit. It is a process of hiding all the internal details of an object from the outside world.
   Example: Capsule: Capsule which hides medicine inside it.
   
   
4. Abstraction: Abstraction means showing only necessary information & hiding unnecessary information from the user. Abstraction let you focus on what object does instead of how it does it.
   Example:Suppose u have a car, and u are riding car, now when you apply break you know that car is going to stop but you don't know what is the process happened when you applied break. Abstraction means putting all the variables and methods in a class that is necessary.
   
   

The sealed class is used to stop the class from being inherited from other classes. If you define a class in C# as "Sealed" & "nonheritable" in VB.NET, then you can not inherit the class further.

Value types directly contain data and derived from System.ValueType.
Value types use the stack to store value.
Example: int, float, char, Bool, short

reference types stored the address of memory where data is stored
reference types use the heap to store value.
Example: Class, Interface, String, Object, Delegate, Array