what is the use of interfaces..??

First and foremost, interfaces in C# are a means to get around the lack of multiple inheritance in C#, meaning you cannot inherit from multiple classes but you can implement multiple interfaces. OOP tries to resemble how objects are defined in the real life, and interfaces are a very logical way of grouping objects in terms of behavior.

An interface is a contract between itself and any class that implements it. This contract states that any class that implements the interface will implement the interface's properties, methods and/or events. An interface contains no implementation, only the signatures of the functionality the interface provides. An interface can contain signatures of methods, properties, indexers & events.

You can think of an interface as an abstract class with the implementation stripped out. An interface doesn't actually do anything, like a class or abstract class, it merely defines what a class that implements it will do. An interface can also inherit/implement other interfaces.

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Bikesh Srivastava10y ago
sontosh kumar is correct.
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Ramesh S10y ago
Interfaces are useful when you cannot use class inheritance.
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Nitin Sontakke10y ago
Answer to following forum question might also be helpful to you!

http://www.c-sharpcorner.com/forums/when-should-you-use-an-interface

http://www.c-sharpcorner.com/forums/real-world-scenario-for-using-interfaces-in-c-sharp

http://www.c-sharpcorner.com/forums/why-access-modifier-is-not-use-in-interface-in-c-sharp

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Santhosh Kumar10y ago
First and foremost, interfaces in C# are a means to get around the lack of multiple inheritance in C#, meaning you cannot inherit from multiple classes but you can implement multiple interfaces. OOP tries to resemble how objects are defined in the real life, and interfaces are a very logical way of grouping objects in terms of behavior.
An interface is a contract between itself and any class that implements it. This contract states that any class that implements the interface will implement the interface's properties, methods and/or events. An interface contains no implementation, only the signatures of the functionality the interface provides. An interface can contain signatures of methods, properties, indexers & events.
You can think of an interface as an abstract class with the implementation stripped out. An interface doesn't actually do anything, like a class or abstract class, it merely defines what a class that implements it will do. An interface can also inherit/implement other interfaces.
+1