using System;

public class Program

{

    public delegate void Del(int x,int y);

    public static void Main()

    {

        var a  = new A();

        Del d= a.Sum();

        d(5,5);

    }

}

public class A{

 public void D1(){

  Console.WriteLine("A D1");

 }

    public virtual void D2(){

  Console.WriteLine("A D2");

 }

    public int Sum(int a,int b){

        Console.WriteLine("A Sum");

        return a+b;

    }

}

​

public class B:A{

 public new void D1(){

  Console.WriteLine("B D1");

 }

 public override void D2(){

  Console.WriteLine("B D2");

 }

}

​