using System;using System.Collections.Generic;public delegate void DExchange
     
      (ref T t1,ref T t2);public interface IExchange
      
       {    void Swap(ref T t1,ref T t2);}public class MyClass
       
        : IExchange
        
         {    public void Swap(ref T t1,ref T t2)    {        T temp = t1;        t1 = t2;        t2 = temp;    }    public void SayHello
         
          (V v1,M m1)    {        return;    }}public class RunMyApp{    public static void Main()    {        string s = "abc";        string t = "efg";        MyClass
          
            my = new MyClass
           
            (); my.Swap(ref s,ref t); IExchange
            
              IE = my; IE.Swap(ref s, ref t); DExchange
             
               de = my.Swap; de(ref s, ref t); Console.WriteLine(s); Console.ReadKey(); }}