设计模式：观察者模式

//报纸接口
   public interface INewsPaper
   {
       //添加订阅者
       void RegisterSubscriber(ISubScribe f_subScribe);
       //取消订阅
       void RemoveSubScriber(ISubScribe f_subScribe);
       //发送报纸
       void SendPaper();
   }
 
   //订阅者
   public interface ISubScribe
   {
       //有新的报纸了就会被执行通知
       void HasNewPaper();
   }
 
   //人民日报
   public class PeopleNewsPaper : INewsPaper
   {
       private List<ISubScribe> subList = new List<ISubScribe>();
       public void RegisterSubscriber(ISubScribe f_subScribe)
       {
           subList.Add(f_subScribe);
       }
 
       public void RemoveSubScriber(ISubScribe f_subScribe)
       {
           if (subList.IndexOf(f_subScribe) >= 0)
           {
               subList.Remove(f_subScribe);
           }
       }
 
       //发报纸啦~~
       public void SendPaper()
       {
           foreach (ISubScribe _sub in subList)
           {
               _sub.HasNewPaper();
           }
       }      
   }
 
   public class subHuman : ISubScribe
   {
       //订阅者的名字
       private string p_name;
 
       public subHuman(string f_name)
       {
           p_name = f_name;
       }
       //告诉订阅者有新报纸了
       public void HasNewPaper()
       {
           Console.WriteLine(p_name + "!! 有新的报纸了，请查收！");
       }
        
   }

开始订订阅，和调用了
static void Main(string[] args)
        {
            PeopleNewsPaper _paper = new PeopleNewsPaper();
            subHuman _XiaoMing = new subHuman("小明");
            subHuman _ZhaoYun = new subHuman("赵云");
            subHuman _LiuBei = new subHuman("刘备");
            //小明订报
            _paper.RegisterSubscriber(_XiaoMing);
            //赵云订报
            _paper.RegisterSubscriber(_ZhaoYun);
            //刘备订报
            _paper.RegisterSubscriber(_LiuBei);
            //有新报纸了
            _paper.SendPaper();
            Console.WriteLine("---------------发完报纸了------------------");
 
            //小明不想订了，取消报纸
            _paper.RemoveSubScriber(_XiaoMing);
            //又有新报纸了  就没有小明的报纸 了
            _paper.SendPaper();
            Console.ReadLine();
        }