Abstract class and Interface in .net

[RogerFielden]

Hello world,

Can anyone suggest me what is Abstract classes and Interface in .Net and how it is to be implemented, and if possible please provide me the difference between them, probably the difference between both of them comes when their definition comes but if still there some important points to be noted down please let me know.

Thanks in Advance

[Khushal]

As per i found on the internet as well as in the book, An abstract class is a special kind of class which cannot be instantiated. It only allows other classes to inherit from the main class but cannot be instantiated.

Whereas,An interface is not a class. It is an entity that is defined by the word Interface. An interface has no implementation; it only has the signature,or else we could say that it is just the definition of the methods without the body.

Here i will provide you the main difference between them is that a class can implement more than one interface in the program but can only inherit from one abstract class.

[Mecurtis]

Difference between Abstract class and interface-

The Abstract class allows concrete methods (methods that have implementation) but interface does not.

An Abstract class can inherit from only one class, but can implement any number of interfaces.

Interface doesn’t allow variables/constants to be declared but abstract class allows for declaration of variables and constants.

[pancham]

Following are some key points related to these two terms that need to remember:
Interface

1. We can achieve multiple inheritance through interface
2. All methods are abstract and there is no implementation.
3. Interfaces are essentially having all method prototypes no definition
4. No access modifiers are allowed.

Abstract class

1. We can achieve only single inheritance and multi-level inheritance
2. Some methods can be concrete.
3. Contain method definitions also.
4. They have access modifiers
5. It can not be instantiated