利用委托实现异步调用

同步调用示例(委托是一个类型安全的,面向对象的指针)

using System;
using System.Threading;

namespace Demo
{
public delegate int Operate(int x, int y);

public class DelegateAsync
{
static int Add(int a, int b)
{
Console.WriteLine ("Add() invoked on thread:{0}\n",
Thread.CurrentThread.GetHashCode ());
Thread.Sleep (5000);
return a + b;
}

static void Main()
{
Console.WriteLine ("Main() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Add() call in Synchronouse mode
Operate op = new Operate (Add);
int answer = op (10, 20);
//after Add() executed, the folow goes on.
Console.Write("After Add() executed, result = {0}",answer);
Console.ReadKey ();
}
}
}

剖析代码的继承关系: 代理Operate经历了3次派生(绿色部分),实现了一个构造和3个虚拟函数(黄色部分).




异步调用方法:线程异步了,但是主线程等待次线程返回才能获得结果,阻塞在EndInvoke上.

using System;
using System.Threading;

namespace Demo
{
public delegate int Operate(int x, int y);

public class DelegateAsync
{
static int Add(int a, int b)
{
Console.WriteLine ("Add() invoked on thread:{0}\n",
Thread.CurrentThread.GetHashCode ());
Thread.Sleep (5000);
return a + b;
}

static void Main()
{
Console.WriteLine ("Main() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Add() call in Synchronouse mode
Operate op = new Operate (Add);
            IAsyncResult result = op.BeginInvoke(10,20,null,null);
Console.WriteLine ("Doing more in Main() exected immediately.");
//the thread susppend on EndInvoke while 'result' is ready!
int answer = op.EndInvoke (result);
Console.Write("After Add() executed, result = {0}",answer);
Console.ReadKey ();
}
}
}

同步调用:如果线程没有返回,不要一直问何时返回,每间隔500ms做该做的事情!!!

using System;
using System.Threading;

namespace Demo
{
public delegate int Operate(int x, int y);

public class DelegateAsync
{
static int Add(int a, int b)
{
Console.WriteLine ("Add() invoked on thread:{0}\n",
Thread.CurrentThread.GetHashCode ());
Thread.Sleep (5000);
return a + b;
}

static void Main()
{
Console.WriteLine ("Main() invoked on thread:{0}\n",
Thread.CurrentThread.GetHashCode ());
//Add() call in Synchronouse mode
Operate op = new Operate (Add);
IAsyncResult result = op.BeginInvoke(10,20,null,null);
//while result is not OK, do it every 500 ms.
while (!result.AsyncWaitHandle.WaitOne(500,true)) {//result.IsCompleted
Console.WriteLine ("Doing more work in Main().");
}
int answer = op.EndInvoke (result);
Console.Write("After Add() executed, result = {0}",answer);
Console.ReadKey ();
}
}
}

线程回调: 好吧,干脆你返回的时候通知我,我该干啥不耽搁!

using System;
using System.Threading;

/// <summary>
/* Main() invoked on thread:1
Main() execute no need to wait any more.
Add() invoked on thread:3
AddComplete() invoked on thread:3
Your Addition is complete.
*/
/// </summary>
namespace Demo
{
public delegate int Operate(int x, int y);

public class DelegateAsync
{
static int Add(int a, int b)
{
Console.WriteLine ("Add() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
Thread.Sleep (5000);
return a + b;
}

static void AddComplete(IAsyncResult ia)
{
Console.WriteLine ("AddComplete() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Get Result value
System.Runtime.Remoting.Messaging.AsyncResult ar=
(System.Runtime.Remoting.Messaging.AsyncResult)ia;
Operate op = (Operate)ar.AsyncDelegate;
Console.WriteLine ("The value is {0}.", op.EndInvoke (ia));
}

static void Main()
{
Console.WriteLine ("Main() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Add() call in Synchronouse mode
Operate op = new Operate (Add);
IAsyncResult result = op.BeginInvoke (10, 20, new AsyncCallback (AddComplete), null);
Console.WriteLine ("Main() execute no need to wait any more.");
Console.ReadKey ();
}
}
}

主线程向次线程传递对象,通知!

using System;
using System.Threading;

/// <summary>
/*

Main() invoked on thread:1
Main() execute no need to wait any more.
Add() invoked on thread:3
AddComplete() invoked on thread:3
The value is 30.
The Main() thread is :1

*/
/// </summary>
namespace Demo
{
public delegate int Operate(int x, int y);

public class DelegateAsync
{
static int Add(int a, int b)
{
Console.WriteLine ("Add() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
Thread.Sleep (5000);
return a + b;
}

static void AddComplete(IAsyncResult ia)
{
Console.WriteLine ("AddComplete() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Get Result value
System.Runtime.Remoting.Messaging.AsyncResult ar=
(System.Runtime.Remoting.Messaging.AsyncResult)ia;
Operate op = (Operate)ar.AsyncDelegate;
Console.WriteLine ("The value is {0}.", op.EndInvoke (ia));
Thread thread = (Thread)ia.AsyncState;
Console.WriteLine ("The Main() thread is :{0}", thread.GetHashCode());
}

static void Main()
{
Console.WriteLine ("Main() invoked on thread:{0}",
Thread.CurrentThread.GetHashCode ());
//Add() call in Synchronouse mode
Operate op = new Operate (Add);
IAsyncResult result = op.BeginInvoke (10, 20,
new AsyncCallback (AddComplete),Thread.CurrentThread);
Console.WriteLine ("Main() execute no need to wait any more.");
Console.ReadKey ();
}
}
}

推荐下博客客户端工具: Download