分析详见：http://lvxingzhelimin.blog.163.com/blog/static/1707165502011101655652697/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            //老板胡汉三
            Boss huhansan = new Boss() ;
            //看股票的同事
            StockObserver tongshi1 = new StockObserver("魏关拆",huhansan);
            NBAObserver tongshi2 = new NBAObserver("易观查",huhansan);

            huhansan.Attach(tongshi1 );
            huhansan.Attach(tongshi2);
            huhansan.Detach(tongshi1);


            //老板回来
            huhansan.SubjectState = "我胡汉三又回来了！";
            //发出通知
            huhansan.Notify();

            Console.Read();
        }
    }
}
//通知者接口
interface Subject
{
    void Attach(Observer observer);
    void Detach(Observer observer);
    void Notify();
    string SubjectState
    {
        get;
        set;
    }
}

//老板类
class Boss :Subject 
{
    //同事列表
    private IList< Observer > observers = new List < Observer >();
    private string action;
    //增加
    public void Attach(Observer observer)
    {
        observers.Add(observer );
    }
    //减少
    public void Detach(Observer observer)
    {
        observers.Remove(observer );
    }
    //通知
    public void Notify()
    {
        foreach (Observer o in observers)
            o.Update();
    }
    //老板类的状态
    public string SubjectState
    {
        get { return action; }
        set { action = value; }
    }
}

//抽象观察者
abstract class  Observer
{
    protected string name;
    protected Subject sub;

    //构造方法,指明观察者姓名建立和通知者间的关联
    public Observer(string name,Subject sub)
    {
        this.name = name;
        this.sub = sub;
    }

    //定义抽象方法——更新
    public abstract void Update();
  
}

//看股票的同事
class StockObserver : Observer
{
    //首先建立与继承的父类的最基本的属性设置
    public StockObserver(string name,Subject sub ):base (name,sub )
    {
    }
    //看股票同事的更新事件，重写父类的Update方法。
    public override void Update()
    {
        Console.WriteLine("{0} {1} 关闭股票行情，继续工作！",sub .SubjectState,name);
    }    
}

//看NBA的同事
class NBAObserver : Observer
{
    //添加一个构造方法，指定看NBA同事这个类的姓名和与之关联的观察者
    public NBAObserver(string name,Subject sub)
        : base(name,sub)
    { 
    }

    //重写更新方法
    public override void Update()
    {
        Console.WriteLine("{0}{1}关闭NBA，继续工作！",name );
    }
}