What is Interface in C#.net ?

What is Interface in C#.net ?

Interface is a type which contains only the signatures/declaration of methods/functions, delegates or events.

Declaration /signature of methods meaning method having no implementation as follows,

void Display(string name);  //By Default interface member is Public

It does not contain implementation of methods. 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. Now external objects using this class know that it has contract by which it can dispose Un-used unmanaged objects. 

Important points to remember about Interface:

a)      Supports multiple interface (Single Class can implement multiple interfaces.)

b)      If a class implements an interface, then it has to provide implementation to all its methods.

c)       Contains declaration / signature of methods only, it does not contain implantation of methods.

d)      It cannot contain Data members like string name.

e)      By Default interface members are Public (We cannot set any access modifier to interface members).

f)       Interface cannot contain constructors.

Example: - Defining an Interface,

   

     interface IDisplay

     {

        string name(string name); //By Default interface members are Public

         int a ; // Error, It cannot contain Data members .  

     }

     class Demo : IDisplay

     {

        public string  name(string name) //Must be declare Public

        {

            return “” + name;

        }

     }

Note: If you know some points about interfaces, that i have missed, please comment. So that i will review and upload.