Delegate与Event的区别[转]

using

System;

using

System.Collections.Generic;

using

System.Linq;

using

System.Text;

namespace

Delegate_vs_Event

{

class

Program

{

public

delegate

string

TestDelegate(

string

input);

public

static

TestDelegatemyDelegate;

public

static

event

TestDelegatemyEvent;

static

void

Main(

string

[]args)

{

///1.在声明委托和事件的类内部，对于Delegate与Event的实例的初始化和调用操作没有任何区别;

myDelegate=

new

TestDelegate(TestEvent);

myEvent=

new

TestDelegate(TestEvent);

myDelegate(

"Delegate"

);

myEvent(

"Event"

);

Subjectsubject=

new

Subject();

Observerob=

new

Observer(subject);

subject.Start();

Console.Read();

}

static

string

TestEvent(

string

param)

{

Console.WriteLine(

"Hello"

+param);

return

string

.Empty;

}

}

class

Subject

{

public

delegate

void

TestHandleForReg(

string

param);

public

event

TestHandleForRegTestHandleEvent;

public

TestHandleForRegTestHandleDelegate;

public

void

Start()

{

Console.WriteLine(

"Callexternalmethodresult:"

);

TestHandleEvent(

"Start"

);

Console.WriteLine();

///2.对于Delegate与Event的实例，其订阅(Subscribe,即+=)或取消订阅(Unsubscribe，即-=)的操作没有任何区别;

TestHandleDelegate+=Method_Subject1;

TestHandleDelegate+=Method_Subject2;

TestHandleDelegate-=Method_Subject2;

TestHandleEvent+=Method_Subject1;

TestHandleEvent+=Method_Subject2;

TestHandleEvent-=Method_Subject2;

Console.WriteLine(

"Callinternalmethodresultby[Delegate]"

);

TestHandleDelegate(

"Delegate"

);

Console.WriteLine();

Console.WriteLine(

"Callinternalmethodresultby[Event]"

);

TestHandleEvent(

"Event"

);

Console.WriteLine();

}

public

void

Method_Subject1(

string

str)

{

Console.WriteLine(

"Method_Subject1"

);

}

public

void

Method_Subject2(

string

str)

{

Console.WriteLine(

"Method_Subject2"

);

}

public

static

string

Static_Method_Subject()

{

return

"Static_Method_Subject"

;

}

}

class

Observer

{

public

Observer(Subjectsubject)

{

subject.TestHandleEvent+=Method_Observer;

subject.TestHandleDelegate+=Method_Observer;

///3.Delegate与Event唯一区别就在于以下2点：Event提供了更严格的封装访问控制，其目的是为了防止其他类破坏委托的多播链,故不允许在声明事件的类外初始化或调用.

///即除了声明Event的类，其它类只能订阅(Subscribe,即+=)或取消订阅(Unsubscribe，即-=)该Event;

////*1*/

///subject.TestHandleEvent=newSubject.TestHandleForReg(Method_Observer);

///subject.TestHandleDelegate=newSubject.TestHandleForReg(Method_Observer);///Error:Theevent'Delegate_vs_Event.Subject.TestHandleEvent'canonlyappearonthelefthandsideof+=or-=(exceptwhenusedfromwithinthetype'Delegate_vs_Event.Subject')

////*2*/

///subject.TestHandleDelegate("test");

///subject.TestHandleEvent("test");///Error:Theevent'Delegate_vs_Event.Subject.TestHandleEvent'canonlyappearonthelefthandsideof+=or-=(exceptwhenusedfromwithinthetype'Delegate_vs_Event.Subject')

}

public

void

Method_Observer(

string

info)

{

Console.WriteLine(

"Observer'smethod["

+info+

"]"

);

}

}

}