C# 設計パターン - オブザーバー パターンの代替サンプル コードの概要

public class Sender 
{   //主办方，此处称为消息发送者}

public class Receiver 
{   //订阅报刊的人，此处称为接受者
   private string _name;   private Subject _sub;   public Receiver(string name, Subject sub)
   {       this._name = name;       this._sub = sub;    
   }
}

public class ReceiverCollection
{   //这个集合维护着订阅报刊的人

   //封装一个订阅人的列表
   private List<Receiver> _receivers = new List<Receiver>();   public List<Receiver> ReceiverList
   {     get
     {       return _receivers;
      }
   }    //管理订阅人:增加一个订阅人，移除一个，统计人数
    public void AddReceiver(Receiver r)
    {       this._receivers.Add(r);
    }    public void RemoveReceiver(Receiver r)
    {       if(this._receivers.Contains(r))           this._receivers.Remove(r);       else 
          throw new ArgumentException("此人未订阅此报刊");
    }    public int ReceiverCount
    {       get
       {          return _receivers.Count;
       }
    }

}

public class Sender 
{   //主办方，此处称为消息发送者

   //要知道分发给哪些人
   private ReceiverCollection _receColl;   public Sender(ReceiverCollection receColl)
   {     this._receColl = receColl;
   }   //主办方确定 分发主题
   public List<Subject> SendingSubjects {get; set;}   //主办方通知多个订阅人
    public void Notify()
    {       //执行更新事件
       UpdateEvent();
    }    //因此需要定义一个主办方在通知订阅人时，执行的更新事件
    //事件搭载各类订阅人在收到主题后的行为！！！
    //当事件触发时，回调搭载的各类订阅人收到主题后的行为！！！
    public delegate void MyEventHandler();    public event EventHandler UpdateEvent;
}

public class Subject
{   //主题话题
   public string Topic {get;set;}   //主题摘要
   public string SubAbstract {get;set;}   //主题内容
   public string Content {get;set;}
}

            ReceiverCollection receColl = new ReceiverCollection();
            Sender sender = new Sender(receColl );
            Subject sportSubject = new Subject()
            {
                Topic = "Sport",
                SubAbstract = "篮球，足球，乒乓球",
                Content = "2018年俄罗斯世界杯，今天晚上国足迎来出线的关键争夺战！"
            };
            sender.SendingSubjects.Add(sportSubject);
            Subject newsSubject = new Subject()
            {
                Topic = "News",
                SubAbstract = "国内大事 国际纵横",
                Content = "十九大，即将召开，请前来参会！"
            };

public interface IResponse
{    void WillDo();   
}public class SportsReceiver:Receiver,IResponse
{   public void WillDo()
   {
      Console.WriteLine("I will watch tv tonight, good luck for gays"); 
   }  public SportsReceiver(string name, Subject subject)
            : base(name, subject)
        {

        }
}public class NewsReceiver:Receiver,IResponse
{   public void WillDo()
   {
      Console.WriteLine("I am going to Beijing to meeting"); 
   }   public NewsReceiver(string name, Subject subject)
            : base(name, subject)
        {

        }
}

//添加一位体育大牛：郝海东receColl.AddReceiver(new SportReceiver("Hao Haidong", sender.newsSubjects[0]));
//添加县长：钱烈贤receColl.AddReceiver(new NewsReceiver("Qian Liexian", sender.newsSubjects[1]));

//要在此处注册订阅者看到消息后的反应foreach(var rece in receColl)
  sender.UpdateEvent += new MyEventHandler(rece.WillDo);

sender.Notify();