委托和事件的区别
2010-03-30 22:16
423 查看
在.NET中,委托和事件是直接相关的.如果你有C++的基础,就不难理解委托的作用,委托要达到的目的基本上同C++中的函数指针是一样的,只是委托是类型安全,具有保护机制的---不会指向一个无效的地址.委托主要有两个应用:回调和事件处理.
事件是通过委托来定义的,定义事件之前要有相应的委托,处理事件的委托有严格规定:1, 必须有两个参数,2.第一个参数是一对象,表示是谁引发的事件,第二个参数是从EventArgs派生的类,它包括了处理事件时所需要的信息.
比如定义一个Click事件:
public delegate void EventHandler (obj o, EevntArsg);
public event EventHandler SimpleEvent;
这样就定义了一个SimpleEvent事件,下面为事件添加处理函数:
SimpleEvent += new EventHandler(OnSimpleEvent);
void OnSimpleEvent(object o, EventArsg e)
{
...
}
经典案例1
using System;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//程序设计:
猫大叫一声,所有的老鼠都开始逃跑,主人被惊醒。(C#语言)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//要求:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//1.要有联动性,老鼠和主人的行为是被动的。
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//2.考虑可扩展性,猫的叫声可能引起其他联动效应。
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//要点:1.
联动效果,运行代码只要执行Cat.Cryed()方法。2. 对老鼠和主人进行抽象
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//评分标准:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<1>.构造出Cat、Mouse、Master三个类,并能使程序运行(2分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<2>从Mouse和Master中提取抽象(5分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<3>联动效应,只要执行Cat.Cryed()就可以使老鼠逃跑,主人惊醒。(3分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
namespace
cmdText
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
/**////
<summary>
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
///
EventCat 的摘要说明。
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
///
</summary>
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
delegate
void SubEventHandler();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
class Subject
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
event SubEventHandler SubEvent;
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
protected
void FireAway()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
if (this.SubEvent
!= null)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.SubEvent();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Cat : Subject
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
void Cry()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine("cat cryed.");
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.FireAway();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
class Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public Observer(Subject sub)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
sub.SubEvent
+= new SubEventHandler(Response);
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
void Response();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Mouse : Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
private
string name;
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public Mouse(string
name, Subject sub) : base(sub)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.name
= name;
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
override
void Response()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine(name
+ " attempt to escape!");
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Master : Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
public
Master(Subject sub) : base(sub){}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
override
void Response()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine("host waken");
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
class Class
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
static
void Main(string[] args)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Cat cat
= new Cat();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Mouse mouse1
= new Mouse("mouse1",
cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Mouse mouse2
= new Mouse("mouse2",
cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Master master
= new Master(cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
cat.Cry();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.Read();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
}
事件是通过委托来定义的,定义事件之前要有相应的委托,处理事件的委托有严格规定:1, 必须有两个参数,2.第一个参数是一对象,表示是谁引发的事件,第二个参数是从EventArgs派生的类,它包括了处理事件时所需要的信息.
比如定义一个Click事件:
public delegate void EventHandler (obj o, EevntArsg);
public event EventHandler SimpleEvent;
这样就定义了一个SimpleEvent事件,下面为事件添加处理函数:
SimpleEvent += new EventHandler(OnSimpleEvent);
void OnSimpleEvent(object o, EventArsg e)
{
...
}
经典案例1
using System;
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//程序设计:
猫大叫一声,所有的老鼠都开始逃跑,主人被惊醒。(C#语言)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//要求:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//1.要有联动性,老鼠和主人的行为是被动的。
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//2.考虑可扩展性,猫的叫声可能引起其他联动效应。
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//要点:1.
联动效果,运行代码只要执行Cat.Cryed()方法。2. 对老鼠和主人进行抽象
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//评分标准:
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<1>.构造出Cat、Mouse、Master三个类,并能使程序运行(2分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<2>从Mouse和Master中提取抽象(5分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
//<3>联动效应,只要执行Cat.Cryed()就可以使老鼠逃跑,主人惊醒。(3分)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/None.gif)
namespace
cmdText
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
/**////
<summary>
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
///
EventCat 的摘要说明。
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
///
</summary>
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
delegate
void SubEventHandler();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
class Subject
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
event SubEventHandler SubEvent;
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
protected
void FireAway()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
if (this.SubEvent
!= null)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.SubEvent();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Cat : Subject
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
void Cry()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine("cat cryed.");
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.FireAway();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
class Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public Observer(Subject sub)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
sub.SubEvent
+= new SubEventHandler(Response);
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
abstract
void Response();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Mouse : Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
private
string name;
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public Mouse(string
name, Subject sub) : base(sub)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
this.name
= name;
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
override
void Response()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine(name
+ " attempt to escape!");
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
class Master : Observer
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
public
Master(Subject sub) : base(sub){}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
public
override
void Response()
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.WriteLine("host waken");
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
class Class
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
static
void Main(string[] args)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockStart.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ContractedSubBlock.gif)
{
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Cat cat
= new Cat();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Mouse mouse1
= new Mouse("mouse1",
cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Mouse mouse2
= new Mouse("mouse2",
cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Master master
= new Master(cat);
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
cat.Cry();
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
Console.Read();
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/InBlock.gif)
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedSubBlockEnd.gif)
}
![](http://www.cnblogs.com/Images/OutliningIndicators/ExpandedBlockEnd.gif)
}
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