策略模式

namespace  Strategy_DesignPattern
{
     using  System;


     abstract   class  Strategy
    {
         abstract   public   void  DoAlgorithm();
    }

     class  FirstStrategy : Strategy
    {
         override   public   void  DoAlgorithm()
        {
            Console.WriteLine( " In first strategy " );
        }
    }

     class  SecondStrategy : Strategy
    {
         override   public   void  DoAlgorithm()
        {
            Console.WriteLine( " In second strategy " );
        }
    }

     class  Context
    {
        Strategy s;
         public  Context(Strategy strat)
        {
            s  =  strat;
        }

         public   void  DoWork()
        {
             //  some of the context's own code goes here
        }

         public   void  DoStrategyWork()
        {
             //  now we can hand off to the strategy to do some 
             //  more work
            s.DoAlgorithm();
        }
    }

     ///   <summary>
     ///     Summary description for Client.
     ///   </summary>
     public   class  Client
    {
         public   static   int  Main( string [] args)
        {
            FirstStrategy firstStrategy  =   new  FirstStrategy();
            Context c  =   new  Context(firstStrategy);
            c.DoWork();
            c.DoStrategyWork();

             return   0 ;
        }
    }
}