事件的使用 代码示例

 

摘自：C#程序设计教程 朱毅华 第134页

 

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

namespace t_Event
{

    //--定义事件包含数据

    class MyEventArgs : EventArgs
    {
        private string strText;

        public MyEventArgs(string StrText)  //--构造函数
        {
            this.strText = StrText;

        }

        public string StrText
        {
            get { return strText; }
            set { strText = value; }
        }

    }

    //--发布事件的类
    class EventSource
    {
        MyEventArgs EvArgs = new MyEventArgs("发布事件");

        //定义委托
        public delegate void EventHandler(object from, MyEventArgs e);

        //定义事件
        public event EventHandler TextOut;

        //--激活事件的方法
        public void TriggerEvent()
        {
            if (TextOut != null)  //--不为空，表示有用户订阅
            {
                TextOut(this, EvArgs);
            }
        }
 

    }

    //--订阅事件的类
    class TestApp
    {
        //--处理事件的静态方法
        public static void CatchEvent(object from, MyEventArgs e)
        {
            Console.WriteLine("调用方法CatchEvent");
            Console.WriteLine("CatchEvent:{0}",e.StrText);
        }

        //处理事件的方法
        public void InstanceCatch(object from, MyEventArgs e)
        {
            Console.WriteLine("调用方法InstanceCatch");
            Console.WriteLine("InstanceEvent:{0}", e.StrText);
        }

        static void Main(string[] args)
        {

            EventSource evsrc = new EventSource();

            //订阅事件
            evsrc.TextOut += new EventSource.EventHandler(CatchEvent);

            evsrc.TriggerEvent();

            Console.WriteLine("1 -------------------------");

            //取消事件
            evsrc.TextOut -= new EventSource.EventHandler(CatchEvent);

            evsrc.TriggerEvent();
            Console.WriteLine("取消事件后，这次什么都没做");
            Console.WriteLine("2 -------------------------");

            TestApp theApp = new TestApp();
            evsrc.TextOut += new EventSource.EventHandler(theApp.InstanceCatch);

            evsrc.TriggerEvent();

            Console.WriteLine("3 -------------------------");

            Console.ReadKey();
       
        }

    }

}