C#编程之委托与事件(二)
我在上一篇文章(C#编程之委托与事件(一) )中通过示例结合的方法介绍了委托,在本文中,我同样以代码示例的方式来介绍C#里的事件机制。
二、事件
1.了解概念
事件就是当对象或类状态发生改变时,对象或类发出的信息或通知。发出信息的对象或类称为"事件源",对事件进行处理的方法称为"接收者",通常事件源在发出状态改变信息时,它并不知道由哪个事件接收者来处理.这就需要一种管理机制来协调事件源和接收者,C++中通过函数指针来完成的.在C#中事件使用委托来为触发时将调用的方法提供类型安全的封装。
在介绍事件之前我们先来了解几个事件的基本概念和几个重要素:
--事件的本质
-事件是特殊的委托实例
-事件关键字:event
--事件的四个要素:
-定义事件
-激发事件
-监听事件
-执行事件
2.事件分析
在.NET中,很多控件都有相关的事件,如Button的Click事件,它能响应鼠标的单击事件。
--定义事件
public delegate void EventHandler(object sender,EventArgs e);
public event EventHandler Click;
--激发事件:单击鼠标
--监听事件
this.button1.Click+=new EventHandler(this.button1_Click);
--执行事件
public void button1_Click(object sender,EventArgs e)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//
实现略
}
上面这个button的Click事件是我们最常见的,这里展示出了整个事件过程。接下来我们来看看一个简单的事件实例。
3.简单实例--怎样定义一个完整的事件机制
一.定义委托
//定义事件委托
public delegate void ChangedEventHandler(object sender, EventArgs e);
二.定义事件
//定义一个委托类型事件
public event ChangedEventHandler Changed;
三.触发事件
//用于触发Changed事件
protected virtual void OnChanged(EventArgs e)
{
if (this.Changed != null)
{
this.Changed(this, e);
}
}
四.侦听事件
MyText myText = new MyText();
myText.Changed += new MyText.ChangedEventHandler(myText_Chenged);
五.事件处理程序
//事件处理程序
private static void myText_Chenged(object sender, EventArgs e)
{
Console.WriteLine("Text属性的值改变:{0}", ((MyText)sender).Text);
}
这就完成了一个完整的事件机制,详细代码如下:
MyText
Program
4.实例解说
现在我们需要设计一个电子邮件程序,当收到电子邮件时,希望将该消息转发到传真机(Fax)和手机(CallPhone);
一.我们需要传递消息则需要定义事件传递的消息类吧,定义如下:
二.定义委托及事件
public delegate void MailMsgEventHandler(object sender,MailMsgEventArgs e);
public event MailMsgEventHandler MailMsg;
完整代码定义如下:
三 .传真和手机的定义:
上面的逻辑处理完毕,下面来看看调用情况:
二、事件
1.了解概念
事件就是当对象或类状态发生改变时,对象或类发出的信息或通知。发出信息的对象或类称为"事件源",对事件进行处理的方法称为"接收者",通常事件源在发出状态改变信息时,它并不知道由哪个事件接收者来处理.这就需要一种管理机制来协调事件源和接收者,C++中通过函数指针来完成的.在C#中事件使用委托来为触发时将调用的方法提供类型安全的封装。
在介绍事件之前我们先来了解几个事件的基本概念和几个重要素:
--事件的本质
-事件是特殊的委托实例
-事件关键字:event
--事件的四个要素:
-定义事件
-激发事件
-监听事件
-执行事件
2.事件分析
在.NET中,很多控件都有相关的事件,如Button的Click事件,它能响应鼠标的单击事件。
--定义事件
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
--激发事件:单击鼠标
--监听事件
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
--执行事件
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/dot.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
3.简单实例--怎样定义一个完整的事件机制
一.定义委托
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
4.实例解说
现在我们需要设计一个电子邮件程序,当收到电子邮件时,希望将该消息转发到传真机(Fax)和手机(CallPhone);
一.我们需要传递消息则需要定义事件传递的消息类吧,定义如下:
1
namespace EventEmail
2
{
3
//事件传递的消息定义
4
public class MailMsgEventArgs:EventArgs
5
{
6
public readonly string from, to, subject, body;
7![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
public MailMsgEventArgs(string from, string to, string subject, string body)
9
{
10
this.from = from;
11
this.to = to;
12
this.subject = subject;
13
this.body = body;
14
}
15
}
16
}
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
二.定义委托及事件
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
1
namespace EventEmail
2
{
3
//定义一委托
4
public delegate void MailMsgEventHandler(object sender,MailMsgEventArgs e);
5![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
6
public class MailManager
7
{
8
public event MailMsgEventHandler MailMsg; //委托类型的事件
9![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
protected virtual void OnMailMsg(MailMsgEventArgs e)
11
{
12
if (this.MailMsg != null)
13
{
14
MailMsg(this, e);
15
}
16
}
17![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
//通过事件传递消息
19
public void SimulateArrivingMsg(string from, string to, string subject, string body)
20
{
21
MailMsgEventArgs e = new MailMsgEventArgs(from, to, subject, body);
22
OnMailMsg(e);
23
}
24
}
25
}
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
三 .传真和手机的定义:
1
namespace EventEmail
2
{
3
/// <summary>
4
/// 传真机
5
/// </summary>
6
public class Fax
7
{
8
private TextBox _tBox;
9
public Fax(MailManager mm, TextBox tBox)
10
{
11
//监听事件
12
//这里的FaxMsg,指的是符合MailMsgEventHandler委托的方法,也就是激发事件后所执行的方法
13
mm.MailMsg += new MailMsgEventHandler(FaxMsg);
14
_tBox = tBox;
15
}
16![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
private void FaxMsg(Object sender, MailMsgEventArgs e)
18
{
19
_tBox.Text += string.Format("消息到传真:{4}来自:{0}{4}发到:{1}{4}主题:{2}{4}内容:{3}{4}{4}", e.from, e.to, e.subject, e.body, Environment.NewLine);
20
}
21![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
22
public void Register(MailManager mm)
23
{
24
mm.MailMsg += new MailMsgEventHandler(FaxMsg);
25
}
26![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
27
public void UnRegister(MailManager mm)
28
{
29
//注销事件
30
mm.MailMsg -= new MailMsgEventHandler(FaxMsg);
31
}
32
}
33
}
-----------------------------------------------------------------------------------------------------------![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
26
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
27
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
28
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
29
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
30
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
31
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
32
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
33
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
1
namespace EventEmail
2
{
3
/// <summary>
4
/// 手机
5
/// </summary>
6
public class CallPhone
7
{
8
private TextBox _tBox;
9
public CallPhone(MailManager mm, TextBox tBox)
10
{
11
mm.MailMsg += new MailMsgEventHandler(CellPhoneMsg);
12
_tBox = tBox;
13
}
14![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
15
private void CellPhoneMsg(Object sender, MailMsgEventArgs e)
16
{
17
_tBox.Text += string.Format("消息到手机:{4}来自:{0}{4}发到:{1}{4}主题:{2}{4}内容:{3}{4}{4}", e.from, e.to, e.subject, e.body,Environment.NewLine);
18
}
19![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
20
public void Register(MailManager mm)
21
{
22
mm.MailMsg += new MailMsgEventHandler(CellPhoneMsg);
23
}
24
public void UnRegister(MailManager mm)
25
{
26
mm.MailMsg -= new MailMsgEventHandler(CellPhoneMsg);
27
}
28
}
29
}
四.客户端调用![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
26
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
27
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
28
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
29
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
上面的逻辑处理完毕,下面来看看调用情况:
1
namespace EventEmail
2
{
3
public partial class Form1 : Form
4
{
5
private Fax fax = null;
6
private CallPhone cell = null;
7
private MailManager mm = null;
8
public Form1()
9
{
10
InitializeComponent();
11
mm = new MailManager();
12
fax = new Fax(mm, txtReceiver);
13
cell = new CallPhone(mm, txtReceiver);
14
}
15![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
16
private void Form1_Load(object sender, EventArgs e)
17
{
18![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
19
}
20![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
21
private void btnSend_Click(object sender, EventArgs e)
22
{
23
mm.SimulateArrivingMsg(txtFrom.Text, txtTo.Text, txtSubject.Text, txtBody.Text);
24
}
25![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
26
private void btnClear_Click(object sender, EventArgs e)
27
{
28
this.txtReceiver.Text = "";
29
}
30
}
31
}
![](https://www.cnblogs.com/Images/OutliningIndicators/None.gif)
2
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
3
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
4
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
5
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
6
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
7
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
8
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
9
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
10
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
11
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
12
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
13
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
14
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
15
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
16
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
17
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
18
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
19
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
20
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
21
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
22
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
23
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
24
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
25
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
26
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
27
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
28
![](https://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
29
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
30
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
31
![](https://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
5 .事件的意义
--有利于消息的传播
--有利于模块之间的松散耦合
注:什么是松散耦合?
就以上面电子邮件程序为例。
--如果没有事件机制,在发送邮件时,就需要去调用Fax,CellPhone的相关方法;
--采用事件机制,在发送邮件时,仅许激发邮件管理器的事件既可,与Fax和CellPhone无关;
也就是说,邮件管理器和Fax、CellPhone之间的依赖关系被解除了。
本文就简单的介绍于此,上面看不太明白的可下示例程序了解;
示例程序在载:EventDemo.rar
------------------------------------------------------------------------------------------------------------