Interfaces in C#

An interface is defined as a syntactical contract that all the classes inheriting the interface should follow. The interface defines the 'what'part of the syntactical contract and the deriving classes define the 'how'part of the syntactical contract.

Interfaces define properties, methods, and events, which are the members of the interface. Interfaces contain only the declaration of the members. It is the responsibility of the deriving class to define the members. It often helps in providing a standard structure that the deriving classes would follow.

Abstract classes to some extent serve the same purpose, however, they are mostly used when only few methods are to be declared by the base class and the deriving class implements the functionalities.

using System;
namespace ArrayApplication
{
    public interface person{
         void name(string n);
         void age(int a );
         void clas(int c);
    }
   
    public class usman : person{
    public  void name(string n){
        Console.WriteLine("Usman name= "+n);
    }
    public void age(int a){
        Console.WriteLine("Usman age= "+a);
    }
    public void clas(int c){
        Console.WriteLine("Usman class= "+c);
    }
    }
   
    public class usama : person{
    public void name(string n){
        Console.WriteLine("Usman name= "+n);
    }
    public void age(int a){
        Console.WriteLine("Usman class= "+a);
    }
    public void clas(int c){
        Console.WriteLine("Usman class= "+c);
    }  
    }
   
   public class test
   {
       public static void Main(String[] args){
           usama obj=new usama();
           obj.name("Usama hussain");
           obj.age(20);
           obj.clas(10);
         
           usman obj1=new usman();
           obj1.name("Usman Siddique");
           obj1.age(21);
           obj1.clas(09);
       }
   }
}

=========================================
using System;
namespace ArrayApplication
{
    public interface abc{
         void fun();
              }

   public class MyArray : abc
   {
                                                         public void fun(){
                                                        Console.WriteLine("this is defination of interface fun");
                                                       }
                                                       static void Main(string[] args){
                                                       MyArray obj=new MyArray();
                                                      obj.fun();
                                                      }    }    }