C# Publisher/Subscriber Pattern, keyword event/delegate

这Subscriber代码可以如下

public class DisplayClock    {        public void Subscribe(Clock theClock)        {             theClock.TimeChange += new Clock.TimeInfoHandler(TimeHasChanged);        }        public void TimeHasChanged(object theClock, TimeInfoEventArgs ti)        {            Console.WriteLine("Current Time: {0}:{1}:{2}", ti.hour.ToString(), ti.minute.ToString(), ti.second.ToString());        }    }

这样，当这个类想订阅信息的时候就可以。。。。

 DisplayClock dc = new DisplayClock(); dc.Subscribe(theClock);

event关键字在event programming中特别有用

public delegate void TimeInfoHandler(object clock, TimeInfoEventArgs timeInformation);public event TimeInfoHandler TimeChange;public void OnTimeChange(object clock, TimeInfoEventArgs timeInformation){    if (TimeChange != null)        TimeChange(clock, timeInformation);}

总体代码如下，网上找的

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Threading;namespace EventDelegate{    public class Clock    {        private int _hour;        private int _minute;        private int _second;        public delegate void TimeInfoHandler(object clock, TimeInfoEventArgs timeInformation);        public event TimeInfoHandler TimeChange;        public void OnTimeChange(object clock, TimeInfoEventArgs timeInformation)        {            if (TimeChange != null)                TimeChange(clock, timeInformation);        }        public void Run()        {            for (; ; )            {                Thread.Sleep(1000);                System.DateTime dt = System.DateTime.Now;                if (dt.Second != _second)                {                    TimeInfoEventArgs timeInformation = new TimeInfoEventArgs(dt.Hour, dt.Minute, dt.Second);                    OnTimeChange(this, timeInformation);                }                _second = dt.Second;                _minute = dt.Minute;                _hour = dt.Hour;            }        }    }    public class TimeInfoEventArgs : EventArgs    {        public TimeInfoEventArgs(int hour, int minute, int second)        {            this.hour = hour;            this.minute = minute;            this.second = second;        }        public readonly int hour;        public readonly int minute;        public readonly int second;    }    public class DisplayClock    {        public void Subscribe(Clock theClock)        {             theClock.TimeChange += new Clock.TimeInfoHandler(TimeHasChanged);        }        public void TimeHasChanged(object theClock, TimeInfoEventArgs ti)        {            Console.WriteLine("Current Time: {0}:{1}:{2}", ti.hour.ToString(), ti.minute.ToString(), ti.second.ToString());        }    }    public class DisplayClock2    {        public void Subscribe(Clock theClock)        {            theClock.TimeChange += new Clock.TimeInfoHandler(TimeHasChanged2);        }        public void TimeHasChanged2(object theClock, TimeInfoEventArgs ti)        {            Console.WriteLine("Current Time - 2: {0}:{1}:{2}", ti.hour.ToString(), ti.minute.ToString(), ti.second.ToString());        }    }        class Program    {               public static void Main()        {            Clock theClock = new Clock();            DisplayClock dc = new DisplayClock();            dc.Subscribe(theClock);            DisplayClock2 dc2 = new DisplayClock2();            dc2.Subscribe(theClock);            theClock.Run();        }    }}

代码中，Clock类是所谓的“消息”，Subscriber可以将事件注册到event中从而得到消息订阅，简单易用