观察者模式-不太理解

/*
 * Created by SharpDevelop.
 * User: home
 * Date: 2013/4/27
 * Time: 15:52
 * 
 * To change this template use Tools | Options | Coding | Edit Standard Headers.
 */
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Observer
{
    class Program
    {
        public static void Main(string[] args)
        {
            Boss huhansan = new Boss();
            //Secretary tongzihe = new Secretary();
            
            StockObserver tongshi1 = new StockObserver("魏关姹", huhansan);
            NBAObserver tongshi2 = new NBAObserver("易管查", huhansan);
            
            huhansan.Attach(tongshi1);
            huhansan.Attach(tongshi2);
            
            huhansan.SubjectState= "我胡汉三又回来啦！！！哈哈哈！！！";
            huhansan.Notify();
            
            Console.ReadKey(true);
        }
    }
    /*class Secretary
    {
        private IList<StockObserver> observers = new List<StockObserver>();
        private string action;
        
        public void Attach(StockObserver observer)
        {
            observers.Add(observer);
        }
        
        public void Notify()
        {
            foreach (StockObserver o in observers)
                o.Update();
        }
        
        public string SecretaryAction
        {
            get { return action; }
            set { action = value; }
        }
    }
    class StockObserver
    {
        private string name;
        private Secretary sub;
        public StockObserver(string name, Secretary sub)
        {
            this.name = name;
            this.sub = sub;
        }
        public void Update()
        {
            Console.WriteLine("{0} {1} 关闭股票行情，继续工作！ ",sub.SecretaryAction, name);
        }
    }
    abstract class Observer
    {
        protected string name;
        protected Secretary sub;
        
        public Observer(string name, Secretary sub)
        {
            this.name = name;
            this.sub = sub;
        }
        
        public abstract void Update();
    }
    
    class StockObserver : Observer
    {
        public StockObserver(string name, Secretary sub) : base(name, sub)
        {
            
        }
        public override void Update()
        {
            Console.WriteLine("{0} {1} 关闭股票行情，继续工作！ ",sub.SecretaryAction, name);
        }
    }
    class NBAObserver : Observer
    {
        public NBAObserver(string name, Secretary sub) : base(name, sub)
        {
            
        }
        public override void Update()
        {
            Console.WriteLine("{0} {1} 关闭NBA，继续工作！ ",sub.SecretaryAction, name);
        }
    }
    
    class Secretary
    {
        private IList<Observer> observers = new List<Observer>();
        private string action;
        
        public void Attach(Observer observer)
        {
            observers.Add(observer);
        }
        public void Detach(Observer observer)
        {
            observers.Remove(observer);
        }
        
        public void Notify()
        {
            foreach (Observer o in observers)
                o.Update();
        }
        
        public string SecretaryAction
        {
            get { return action; }
            set { action = value; }
        }
    }*/
    
    interface Subject
    {
        void Attach(Observer observer);
        void Detach(Observer observer);
        void Notify();
        
        string SubjectState
        {
            get;
            set;
        }
    }
    
    class Boss : Subject
    {
        private IList<Observer> observers = new List<Observer>();
        private string action;
        
        public void Attach(Observer observer)
        {
            observers.Add(observer);
        }
        
        public void Detach(Observer observer)
        {
            observers.Remove(observer);
        }
        
        public void Notify()
        {
            foreach (Observer o in observers)
                o.Update();
        }
        
        public string SubjectState
        {
            get { return action; }
            set { action = value; }
        }
    }
    
    
    abstract class Observer
    {
        protected string name;
        protected Subject sub;
        
        public Observer(string name, Subject sub)
        {
            this.name = name;
            this.sub = sub;
        }
        
        public abstract void Update();
    }
    
    class StockObserver : Observer
    {
        public StockObserver(string name, Subject sub) : base(name, sub)
        {
        }
        
        public override void Update()
        {
            Console.WriteLine("{0} {1} 关闭股票行情，继续工作！ ",sub.SubjectState, name);
        }
    }
    
    class NBAObserver : Observer
    {
        public NBAObserver(string name, Subject sub) : base(name, sub)
        {
            
        }
        public override void Update()
        {
            Console.WriteLine("{0} {1} 关闭NBA，继续工作！ ",sub.SubjectState, name);
        }
    }
}