代理模式与装饰者模式很像，起到一定的解耦作用

UML图：

示例代码：

public abstract class Person    {        public abstract void Buy();    }

public class RealBuyUser:Person    {        public override void Buy()        {            Console.WriteLine("我要买盒烟");        }    }

public class Friend:Person    {        private RealBuyUser realBuyUser;        public Friend(RealBuyUser realUser)        {            this.realBuyUser = realUser;        }        public override void Buy()        {            PreBuy();            realBuyUser.Buy();        }        public void PreBuy()        {            Console.WriteLine("帮别人买之前我要佣金");        }    }

class Program    {        static void Main(string[] args)        {            Friend friend =new Friend(new RealBuyUser());            friend.Buy();        }    }