代理模式

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();
        }
    }