委托[delegate]_C#

委托（delegate）:

委托声明定义了一种类型，它用一组特定的参数以及返回类型来封装方法。对于静态方法，委托对象封装要调用的方法。对于实例方法，委托对象同时封装一个实例和该实例上的一个方法。如果您有一个委托对象和一组适当的参数，则可以用这些参数调用该委托。

下面看一段代码：

using System ;

delegate void EatDelegate(string food);

class MyDelegate

{

static void zsEat(string food)

{

Console .WriteLine ("张三吃"+food);

}

static void lsEat(string food)

{

Console .WriteLine ("李四吃"+food);

}

static void wwEat(string food)

{

Console .WriteLine ("王五吃"+food);

}

static void Main()

{

EatDelegate zs=new EatDelegate (zsEat );         //C#2.0语法：

EatDelegate zs=zsEat ;

EatDelegate ls=new EatDelegate (lsEat );

EatDelegate ww=new EatDelegate (wwEat );

EatDelegate eatChain=null;

Console .WriteLine ("座谈会开始");

eatChain = zs+ls+ww;

eatChain ("西瓜");

Console .WriteLine ("李四出去接电话");

eatChain -=ls;

eatChain ("香蕉");

Console .WriteLine ("李四回来了");

eatChain +=ls;

eatChain ("桔子");

//下面是匿名方法¨

eatChain += delegate(string food) {Console .WriteLine ("我吃"+food);   };

eatChain += delegate(string food) {Console .WriteLine ("你吃"+food);   };

eatChain += delegate(string food) {Console .WriteLine ("他吃"+food);   };

eatChain ("饭");

}

}

下面是实例方法的一段代码：

using System ;

delegate void EatDelegate(string food);

class Man

{

private string name;

public Man(string name)

{

this .name =name ;

}

public void eat(string food)

{

Console .WriteLine (name+"吃"+food);

}

}

class Party

{

static void Main()

{

Man ZS=new Man ("张三");

Man LS=new Man ("李四");

Man WW=new Man ("王五");

EatDelegate zs=new EatDelegate (ZS.eat );

EatDelegate ls=new EatDelegate (LS.eat );

EatDelegate ww=new EatDelegate (WW.eat );

EatDelegate eatChain=null;

Console .WriteLine ("座谈会开始");

eatChain = zs+ls+ww;

eatChain ("西瓜");

Console .WriteLine ("李四出去接电话");

eatChain -=ls;

eatChain ("香蕉");

Console .WriteLine ("李四回来了");

eatChain +=ls;

eatChain ("桔子");

}

}

委托可作为方法的参数进行动态调用，看下面代码：

using System ;

delegate void EatDelegate(string food);

class Man

{

private string name;

public Man(string name)

{

this .name =name ;

}

public void eat(string food)

{

Console .WriteLine (name+"吃"+food);

}

}

class Party

{

static void eatTogether(string food,params EatDelegate [] values)

{

if (values ==null )

{

Console .WriteLine ("座谈会结束");

}

else

       {

EatDelegate eatChain=null ;

foreach (EatDelegate ed in values )

eatChain +=ed;

eatChain (food);

Console .WriteLine ();

}

}

static void Main()

{

Man ZS=new Man ("张三");

Man LS=new Man ("李四");

Man WW=new Man ("王五");

EatDelegate zs=new EatDelegate (ZS.eat );

EatDelegate ls=new EatDelegate (LS.eat );

EatDelegate ww=new EatDelegate (WW.eat );

Console .WriteLine ("座谈会开始");

eatTogether("西瓜",zs,ls,ww);

Console .WriteLine ("李四出去接电话");

eatTogether("香蕉",zs,ww);

Console .WriteLine ("李四回来了");

eatTogether("桔子",zs,ls,ww);

Console .WriteLine ("座谈会结束");

eatTogether (null ,null );

}

}