What is a Interface in C# .Net

Interface is a type which contains only the signatures of methods, delegates or events, it has no implementation.
Implementation of the methods is done by the class that which implements the interface.

Interface is a contract that defines the signature of the functionality. So if a class is implementing a interface it says to the outer world, that it provides specific behavior. Example if a class is implementing ‘Idisposable’ interface that means it has a functionality to release unmanaged resources.

If a class implements a interface then it has to provide implementation to all its methods.

Properties Of Interface:-

  • Supports multiple inheritance(Single Class can implement multiple interfaces).
  • Contains only incomplete method.
  • Can not Contains data members.
  • By Default interface members is public (We Can not set any access modifier into interface members).
  •  Interface can not contain constructors.

Example :- Defining an Interface:

     interface IApp
     {
       int Sum(int i, int j); //By Default Public
     }
     class App : IApp
     {
        public int sum(int i, int j) //Must be declare Public
        {
           return i + j;
        }
     }

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