事件与委托 echo

客户端代码：

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

namespace EventDemo
{
    class Program
    {
        static void Main(string[] args)
        {
            //创建一个出版社
            Publisher publisher = new Publisher("清华大学出版社");

            //创建两个订阅者
            Subscripter nicholas = new Subscripter("Nicholas");
            Subscripter eric = new Subscripter("Eric");

            //注册事件 (添加委托链)
            publisher.PubComputer += new Publisher.PubComputerEventHandler(nicholas.Receive);
            publisher.PubLive += new Publisher.PubLiveEventHandler(nicholas.Receive);         
            publisher.PubLive += new Publisher.PubLiveEventHandler(eric.Receive);

            //触发发行动作
            publisher.IssueComputer("《Begining C# Editon 7》", DateTime.Parse("2010-10-01"), "99.90$");
            publisher.IssueLive("《Our Life》", DateTime.Parse("2010-10-01"), "18.00$");

            Console.WriteLine("Eric由于订阅金额不足，不予订阅！\r\n");
            publisher.PubLive -= new Publisher.PubLiveEventHandler(eric.Receive);

            publisher.IssueComputer("《Begining C# Editon 7》", DateTime.Parse("2012-03-01"), "99.90$");
            publisher.IssueLive("《Our Life》", DateTime.Parse("2012-03-01"), "18.00$");

            Console.ReadKey();
        }
    }
}

/* ======编写事件、委托程序步骤=====
 * 
 * 1、确定事件源（事件发送者）和事件接受者（订阅者）
 * 2、在事件源中声明与该事件所关联的delegate委托，接着声明该事件，类型为委托类型
 * 3、在事件源中编写触发事件的方法，判断该事件是否为null（是否注册事件），若不为null，则执行该事件
 * 4、编写一个类，该类继承EventArgs，在该类中定义事件所需的一些参数
 * 5、在接受者中编写事件处理程序（方法），该方法包含两个参数（object sender, XXXEventArgs e），即与之前定义的委托签名一致
 * 6、在客户端注册事件（委托链+=）
 * 7、在客户端调用触发事件的方法
 * */

事件源（事件发布者）：

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

namespace EventDemo
{
    /// <summary>
    /// 出版社
    /// </summary>
    public class Publisher
    {
        private string publisherName;

        /// <summary>
        /// 出版社名称
        /// </summary>
        public string PublisherName
        {
            get { return publisherName; }
            set { publisherName = value; }
        }

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="publisherName">出版社名称</param>
        public Publisher(string publisherName)
        {
            this.publisherName = publisherName;
        }

        /// <summary>
        /// 发行计算机杂志delegate
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        public delegate void PubComputerEventHandler(object sender, PubEventArgs e);

        /// <summary>
        /// 发行计算机杂志event
        /// </summary>
        public event PubComputerEventHandler PubComputer;

        /// <summary>
        /// 发行生活杂志delegate
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        public delegate void PubLiveEventHandler(object sender, PubEventArgs e);

        /// <summary>
        /// 发行生活杂志event
        /// </summary>
        public event PubLiveEventHandler PubLive;

        /// <summary>
        /// 出版社发布计算机杂志方法
        /// <param name="e">发生事件时的参数</param>
        /// </summary>
        protected virtual void OnPubComputer(PubEventArgs e)
        {
            //PubComputerEventHandler delHandler = this.PubComputer;
            if (this.PubComputer != null)
            {
                this.PubComputer(this, e);
            }
            else
            {
                Console.WriteLine("该杂志没有用户订阅");
            }
        }

        /// <summary>
        /// 出版社发布生活杂志方法
        /// <param name="e">发生事件时的参数</param>
        /// </summary>
        protected virtual void OnPubLive(PubEventArgs e)
        {
            //PubLiveEventHandler delHandler = this.PubLive;
            if (this.PubLive != null)
            {
                this.PubLive(this, e);
            }
            else
            {
                Console.WriteLine("该杂志没有用户订阅");
            }
        }
                     
        /// <summary>
        ///  触发计算机杂志事件
        /// </summary>
        /// <param name="name">杂志名称</param>
        /// <param name="issueTime">发行时间</param>
        /// <param name="price">定价</param>
        public void IssueComputer(string name, DateTime issueTime, string price)
        {
            Console.WriteLine("出版社发行：" + name + " 杂志");
            this.OnPubComputer(new PubEventArgs(name, issueTime, price));
        }

        /// <summary>
        ///  触发计生活杂志事件
        /// </summary>
        /// <param name="name">杂志名称</param>
        /// <param name="issueTime">发行时间</param>
        /// <param name="price">定价</param>
        public void IssueLive(string name, DateTime issueTime, string price)
        {
            Console.WriteLine("出版社发行：" + name + " 杂志");
            this.OnPubLive(new PubEventArgs(name, issueTime, price));
        }
    }

    /// <summary>
    /// 发生事件是的参数
    /// </summary>
    public class PubEventArgs : EventArgs
    {
        private readonly string pubName;
        private readonly DateTime pubDateTime;
        private readonly string price;

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="pubName">发行名称</param>
        /// <param name="pubDateTime">发行时间</param>
        /// <param name="price">定价</param>
        public PubEventArgs(string pubName, DateTime pubDateTime, string price)
        {
            this.pubName = pubName;
            this.pubDateTime = pubDateTime;
            this.price = price;
        }

        /// <summary>
        /// 杂志的名称
        /// </summary>
        public string PubName
        {
            get { return pubName; }
        }

        /// <summary>
        /// 发行的日期
        /// </summary>
        public DateTime PubDateTime
        {
            get { return pubDateTime; }
        }

        /// <summary>
        /// 该杂志的定价
        /// </summary>
        public string Price
        {
            get { return price; }
        } 
    }
}

事件订阅者：

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

namespace EventDemo
{
    /// <summary>
    /// 杂志订阅者
    /// </summary>
    public class Subscripter
    {
        private string name;

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="name">the full name of subscripter</param>
        public Subscripter(string name)
        {
            this.name = name;
        }

        /// <summary>
        /// 杂志订阅者的事件处理
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        public void Receive(object sender, PubEventArgs e)
        {
            Publisher pub = (Publisher)sender;

            Console.WriteLine("{0} 已经收到了由{1}" + "发行的杂志：{2},\r\n发行日期：{3},\r\n" + "定价：{4}\r\n",
                name, pub.PublisherName, e.PubName, e.PubDateTime.ToShortDateString(), e.Price);
            Console.WriteLine();
        }
    }
}

执行结果：