delegate(委托)、event(事件) 的基础知识

1. event和delegate类型的字段到底有什么区别

 

http://www.cnblogs.com/Microshaoft/archive/2005/05/30/164753.html

 

2. 事件与事件处理程序

a)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;

namespace WebApplication14
{
    public partial class _Default : System.Web.UI.Page
    {
        private static StringBuilder mysb = new StringBuilder();
        protected void Page_Load(object sender, EventArgs e)
        {
            HasEvent he = new HasEvent();
           
            he.SampleEvent += new HasEvent.MyEventHandler(SampleEventHandler);

            he.DemoEvent("Hey there, Bruce!");
            he.DemoEvent("How are you today?");
            he.DemoEvent("I'm pretty good.");
            he.DemoEvent("Thanks for asking!");
            Label1.Text = mysb.ToString() ;
        }

        private static void SampleEventHandler(object src, MyEventArgs mea)
        {
            mysb.Append(mea.Message);
        }
    }

    public class MyEventArgs : EventArgs
    {
        private string msg;

        public MyEventArgs(string messageData)
        {
            msg = messageData;
        }
        public string Message
        {
            get { return msg; }
            set { msg = value; }
        }
    }
    //---------------------------------------------------------
    public class HasEvent
    {
        // Declare an event of delegate type MyEventHandler of 
        // MyEventArgs.

        
        public delegate void MyEventHandler(object sender, MyEventArgs e);
        public event MyEventHandler SampleEvent;

        public void DemoEvent(string val)
        {
            // Copy to a temporary variable to be thread-safe.
            
            MyEventHandler temp = SampleEvent;
            if (temp != null)
                temp(this, new MyEventArgs(val));
        }
    }
}

 

b)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;

namespace WebApplication14
{
    public partial class _Default : System.Web.UI.Page
    {
        private static StringBuilder mysb = new StringBuilder();
        protected void Page_Load(object sender, EventArgs e)
        {
            HasEvent he = new HasEvent();
            he.SampleEvent +=
                       new EventHandler<MyEventArgs>(SampleEventHandler);  

            he.DemoEvent("Hey there, Bruce!");
            he.DemoEvent("How are you today?");
            he.DemoEvent("I'm pretty good.");
            he.DemoEvent("Thanks for asking!");
            Label1.Text = mysb.ToString() ;
        }

        private static void SampleEventHandler(object src, MyEventArgs mea)
        {
            mysb.Append(mea.Message);
        }
    }

    public class MyEventArgs : EventArgs
    {
        private string msg;

        public MyEventArgs(string messageData)
        {
            msg = messageData;
        }
        public string Message
        {
            get { return msg; }
            set { msg = value; }
        }
    }
    //---------------------------------------------------------
    public class HasEvent
    {
        // Declare an event of delegate type EventHandler of 
        // MyEventArgs.

        public event EventHandler<MyEventArgs> SampleEvent;        

        public void DemoEvent(string val)
        {
            // Copy to a temporary variable to be thread-safe.
            EventHandler<MyEventArgs> temp = SampleEvent;           
            if (temp != null)
                temp(this, new MyEventArgs(val));
        }
    }
}

 

c) 假定用户控件(UserControl.ascx)中包含按钮控件Save，希望实现按Save按钮时，包含该用户控件的页面(Default.aspx)可以接收到事件。

UserControl.ascx.cs

public event EventHandler SaveClick;

        protected void Save_Click(object sender, EventArgs e)
        {
            if (SaveClick != null)
                SaveClick(this, e);
        }

 

Default.aspx.cs 代码

<uc1:WebUserControl1 ID="WebUserControl11" runat="server" OnSaveClick="Save_Click" />

 protected void Save_Click(object sender, EventArgs e)
 {           
 }