Delegate比较全面的例子
2006-08-30 15:47
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将Delegate理解为接口,只有一个方法的接口,这样最容易理解。这个方法只有声明,没有实现,实现在别的类。(实际上应该把它看作函数指针,不过接口更容易理解些。)
在你的类中有一个Delegate就相当于有一个接口。通过这个接口你可以调用一个方法,而这个方法在别的类定义,由别的类来干。
为了说的形象一点,举个例子:
学生考试完后成绩出来了,考的好了老师要表扬,考的不好了老师要批评。
使用接口的方法:
[align=left]
using System; [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] private IAdviser adviser; [/align]
[align=left] [/align]
[align=left] public void SetAdviser(IAdviser iadviser) [/align]
[align=left] { [/align]
[align=left] adviser = iadviser; [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (adviser != null) [/align]
[align=left] { [/align]
[align=left] string result = adviser.Advise(score); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]
public interface IAdviser [/align]
[align=left]{ [/align]
[align=left] string Advise(int score); [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher : IAdviser [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] if (score < 60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] private static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] IAdviser teacher = new Teacher(); [/align]
[align=left] Student s = new Student(); [/align]
[align=left] s.SetAdviser(teacher); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]} [/align]
使用Delegate的方法:
[align=left]using System; [/align]
[align=left]using System.Threading; [/align]
[align=left] [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] string result=AdviseDelegateInstance(score); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] public delegate string AdviseDelegate(int score); [/align]
[align=left] [/align]
[align=left] public AdviseDelegate AdviseDelegateInstance; [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] if(score<60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] Teacher teacher=new Teacher(); [/align]
[align=left] Student s=new Student(); [/align]
[align=left] [/align]
[align=left] s.AdviseDelegateInstance=new Student.AdviseDelegate(teacher.Advise); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]}
[/align]
如果老师很忙不能及时回复怎么办?比如这样:
[align=left]但是它不能使用带参数的函数,怎么办?(谁知道方法请指教)
.Net2.0提供了新的方法ParameterizedThreadStart
[/align]
[align=left]
用Delegate解决(异步调用): [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score,null,null); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]不过这样我们失去了老师的返回结果,不知道有没有及格了。 [/align]
[align=left]采用轮讯的方法去获得结果: [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] [/align]
[align=left] IAsyncResult res = AdviseDelegateInstance.BeginInvoke(score,null, null); [/align]
[align=left] [/align]
[align=left] while( !res.IsCompleted ) System.Threading.Thread.Sleep(1); [/align]
[align=left] [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(res); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]不过这样主线程又被阻塞了,采用回调的方式: (注:接口也可以采用回调的方式获得返回值) [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] IAsyncResult res = AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), null); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t" + result); [/align]
[align=left] }
[/align]
[align=left]
这样就比较得到了一个比较好的解决方案了。我们再来看看BeginInvoke的第四个参数是干吗的呢? [/align]
[align=left]
public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] string stateObj=(string)asyncResult.AsyncState; [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生{0}收到老师返回的结果/t" + result,stateObj.ToString()); [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]哦,原来它可以用来标记调用者的一些信息。(这里采取的是硬编码的方式,你可以把它改为学生的id之类的信息)。
[/align]
[align=left]
总结:Delegate类似与Interface但是功能更加强大和灵活,它甚至还可以绑定到Static方法只要函数签名一致,而且由于+=操作符的功能,实现多播也是极为方便(即Observer模式),在此不再举例。
[/align]
(补充:多播的时候改一下SetScore函数)
[align=left]本文没什么新的内容,就是自己练一下手,写个总结材料,希望对大家有帮助。.net2.0提供了更好的线程模型。[/align]
[align=left] [/align]
[align=left]完整源代码如下: [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] foreach( AdviseDelegate ad in AdviseDelegateInstance.GetInvocationList()) [/align]
[align=left] { [/align]
[align=left] ad.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]using System; [/align]
[align=left]using System.Threading; [/align]
[align=left] [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] string stateObj=(string)asyncResult.AsyncState; [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生{0}收到老师返回的结果/t" + result,stateObj); [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] public delegate string AdviseDelegate(int score); [/align]
[align=left] [/align]
[align=left] public AdviseDelegate AdviseDelegateInstance; [/align]
[align=left] [/align]
[align=left] [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] Thread.Sleep(3000); [/align]
[align=left] if (score < 60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score + "老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score + "老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] private static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] Teacher teacher = new Teacher(); [/align]
[align=left] Student s = new Student(); [/align]
[align=left] [/align]
[align=left] s.AdviseDelegateInstance= new Student.AdviseDelegate(teacher.Advise); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]}
[/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] Thread.Sleep(3000); [/align]
[align=left] if(score<60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]}
总不能让学生一直等下去吧,采用多线程并发的办法。
Interface的解决办法:
public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (adviser != null) [/align]
[align=left] { [/align]
[align=left] Thread.adviserThread=new Thread(new ThreadStart(adviser.Advise())); [/align]
[align=left] adviserThread.Start(); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]
[/align]
在你的类中有一个Delegate就相当于有一个接口。通过这个接口你可以调用一个方法,而这个方法在别的类定义,由别的类来干。
为了说的形象一点,举个例子:
学生考试完后成绩出来了,考的好了老师要表扬,考的不好了老师要批评。
使用接口的方法:
[align=left]
using System; [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] private IAdviser adviser; [/align]
[align=left] [/align]
[align=left] public void SetAdviser(IAdviser iadviser) [/align]
[align=left] { [/align]
[align=left] adviser = iadviser; [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (adviser != null) [/align]
[align=left] { [/align]
[align=left] string result = adviser.Advise(score); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]
public interface IAdviser [/align]
[align=left]{ [/align]
[align=left] string Advise(int score); [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher : IAdviser [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] if (score < 60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] private static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] IAdviser teacher = new Teacher(); [/align]
[align=left] Student s = new Student(); [/align]
[align=left] s.SetAdviser(teacher); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]} [/align]
使用Delegate的方法:
[align=left]using System; [/align]
[align=left]using System.Threading; [/align]
[align=left] [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] string result=AdviseDelegateInstance(score); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] public delegate string AdviseDelegate(int score); [/align]
[align=left] [/align]
[align=left] public AdviseDelegate AdviseDelegateInstance; [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] if(score<60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] Teacher teacher=new Teacher(); [/align]
[align=left] Student s=new Student(); [/align]
[align=left] [/align]
[align=left] s.AdviseDelegateInstance=new Student.AdviseDelegate(teacher.Advise); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]}
[/align]
如果老师很忙不能及时回复怎么办?比如这样:
[align=left]但是它不能使用带参数的函数,怎么办?(谁知道方法请指教)
.Net2.0提供了新的方法ParameterizedThreadStart
[/align]
[align=left]
用Delegate解决(异步调用): [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score,null,null); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]不过这样我们失去了老师的返回结果,不知道有没有及格了。 [/align]
[align=left]采用轮讯的方法去获得结果: [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] [/align]
[align=left] IAsyncResult res = AdviseDelegateInstance.BeginInvoke(score,null, null); [/align]
[align=left] [/align]
[align=left] while( !res.IsCompleted ) System.Threading.Thread.Sleep(1); [/align]
[align=left] [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(res); [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t"+result); [/align]
[align=left] [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]不过这样主线程又被阻塞了,采用回调的方式: (注:接口也可以采用回调的方式获得返回值) [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] IAsyncResult res = AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), null); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生收到老师返回的结果/t" + result); [/align]
[align=left] }
[/align]
[align=left]
这样就比较得到了一个比较好的解决方案了。我们再来看看BeginInvoke的第四个参数是干吗的呢? [/align]
[align=left]
public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] string stateObj=(string)asyncResult.AsyncState; [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生{0}收到老师返回的结果/t" + result,stateObj.ToString()); [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]哦,原来它可以用来标记调用者的一些信息。(这里采取的是硬编码的方式,你可以把它改为学生的id之类的信息)。
[/align]
[align=left]
总结:Delegate类似与Interface但是功能更加强大和灵活,它甚至还可以绑定到Static方法只要函数签名一致,而且由于+=操作符的功能,实现多播也是极为方便(即Observer模式),在此不再举例。
[/align]
(补充:多播的时候改一下SetScore函数)
[align=left]本文没什么新的内容,就是自己练一下手,写个总结材料,希望对大家有帮助。.net2.0提供了更好的线程模型。[/align]
[align=left] [/align]
[align=left]完整源代码如下: [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] foreach( AdviseDelegate ad in AdviseDelegateInstance.GetInvocationList()) [/align]
[align=left] { [/align]
[align=left] ad.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left]using System; [/align]
[align=left]using System.Threading; [/align]
[align=left] [/align]
[align=left]public class Student [/align]
[align=left]{ [/align]
[align=left] private int score; [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (AdviseDelegateInstance!= null) [/align]
[align=left] { [/align]
[align=left] AdviseDelegateInstance.BeginInvoke(score, new System.AsyncCallback(CallBackMethod), "idior"); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] private void CallBackMethod(IAsyncResult asyncResult) [/align]
[align=left] { [/align]
[align=left] string result = AdviseDelegateInstance.EndInvoke(asyncResult); [/align]
[align=left] string stateObj=(string)asyncResult.AsyncState; [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生{0}收到老师返回的结果/t" + result,stateObj); [/align]
[align=left] } [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] public delegate string AdviseDelegate(int score); [/align]
[align=left] [/align]
[align=left] public AdviseDelegate AdviseDelegateInstance; [/align]
[align=left] [/align]
[align=left] [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] Thread.Sleep(3000); [/align]
[align=left] if (score < 60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score + "老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score + "老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]} [/align]
[align=left] [/align]
[align=left]class MainClass [/align]
[align=left]{ [/align]
[align=left] [STAThread] [/align]
[align=left] private static void Main(string[] args) [/align]
[align=left] { [/align]
[align=left] Teacher teacher = new Teacher(); [/align]
[align=left] Student s = new Student(); [/align]
[align=left] [/align]
[align=left] s.AdviseDelegateInstance= new Student.AdviseDelegate(teacher.Advise); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("学生得到50分"); [/align]
[align=left] s.SetScore(50); [/align]
[align=left] [/align]
[align=left] Console.Out.WriteLine("/n学生得到75分"); [/align]
[align=left] s.SetScore(75); [/align]
[align=left] [/align]
[align=left] [/align]
[align=left] Console.ReadLine(); [/align]
[align=left] } [/align]
[align=left]}
[/align]
[align=left]public class Teacher [/align]
[align=left]{ [/align]
[align=left] public string Advise(int score) [/align]
[align=left] { [/align]
[align=left] Thread.Sleep(3000); [/align]
[align=left] if(score<60) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说加油"); [/align]
[align=left] return "不及格"; [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine(score+"老师说不错"); [/align]
[align=left] return "及格"; [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]}
总不能让学生一直等下去吧,采用多线程并发的办法。
Interface的解决办法:
public void SetScore(int value) [/align]
[align=left] { [/align]
[align=left] if (value > 100 || value < 0) [/align]
[align=left] { [/align]
[align=left] Console.Out.WriteLine("分数不对"); [/align]
[align=left] } [/align]
[align=left] else [/align]
[align=left] { [/align]
[align=left] score = value; [/align]
[align=left] if (adviser != null) [/align]
[align=left] { [/align]
[align=left] Thread.adviserThread=new Thread(new ThreadStart(adviser.Advise())); [/align]
[align=left] adviserThread.Start(); [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left] } [/align]
[align=left]
[/align]
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