InterFace

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;


interface ICalculate
{
    void IADD();
    void ISUB();
    
}


class Calculate : ICalculate /////////Child class Calculate Inherited Interface ICalculate
{
    #region ICalculate Members


    public void IADD()
    {
        //throw new System.NotImplementedException();


        int x, y, z;
        Console.WriteLine("Enter values for x and y");
        x = int.Parse(Console.ReadLine());
        y = Convert.ToInt32(Console.ReadLine());
        z = x + y;
        Console.WriteLine("Addition of x and y is: " + z);


    }


    public void ISUB()
    {
       // throw new System.NotImplementedException();


        int x, y, r;
        Console.WriteLine("Enter values for x and y");
        x = int.Parse(Console.ReadLine());
        y = Convert.ToInt32(Console.ReadLine());
       r = x - y;
        Console.WriteLine("Subtraction of x and y is: " +r);




    }


    
   #endregion
}

//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

namespace Interface

{

    class Program

    {

        static void Main(string[] args)

        {

            

            Console.WriteLine("An interface looks like a class, but has no implementation. The only thing it contains are declarations of events, indexers, methods and/or properties. The reason interfaces only provide declarations is because they are inherited by classes and structs, which must provide an implementation for each interface member declared.");

            Console.WriteLine();

            Console.WriteLine("C# does not support multiple inheritence to overcome these problems we use interfaces. This is main use of Interfaces we have in C#.");

            Console.WriteLine();

            Console.WriteLine("Interfaces are a very logical way of grouping objects in terms of behavior. ");

            Console.WriteLine();

            ICalculate obj = new Calculate();/////Instance ie representative of Interface and Abstract class cannot be created

                                              /////ICalculate obj = new ICalculate();

                                              ////// object of interface is a representative of Class Calculate 

                                              ////// Break Point cannot be allocated for interface for debugging.

            obj.IADD();

            obj.ISUB();

            

            

            //Console.WriteLine("Division of 2 nos is");

            //Console.WriteLine("" + obj.IDIV(10,2));

        }

    }

}