多线程之异步编程模式

.Net为执行异步操作提供了三中模式：

• 异步编程模型 (APM)
• 基于事件的异步模式(EAP)
• 基于任务的异步模式(TAP)

1.异步编程模型(APM)。

使用IAsyncResult设计模式的异步操作通过Begin操作和End操作两个方法实现。

在调用Begin操作后，调用线程继续执行指令，同时异步操作在另外一个线程上执行，调用线程调用End方法来获取结果。

Code：

 1 namespace Examples
 2 {
 3     public class Progrom
 4     {
 5         public static void Main()
 6         {
 7             AsyncWorkTest work = new AsyncWorkTest();
 8             IAsyncResult result = work.BeginWork(CallBack, null);
 9             Console.WriteLine("Work is begining...");
10             string ret = work.EndWork(result);
11             Console.WriteLine(ret);
12             Console.WriteLine("Work is end...");
13             Console.ReadKey();
14         }
15 
16         static void CallBack(object obj)
17         {
18             //do someing
19         }
20     }
21 
22     public class AsyncResult : IAsyncResult
23     {
24         public AsyncResult()
25         {
26             //Accept parameters
27         }
28         private object asyncState;
29         private volatile bool isCompleted;
30         private volatile bool completedSynchronously;
31         private ManualResetEvent asynWaitHandle;
32 
33         public string Result = "Mandel";
34 
35         public object AsyncState
36         {
37             get { return asyncState; }
38         }
39         public WaitHandle AsyncWaitHandle
40         {
41             get
42             {
43                 if (this.asynWaitHandle == null)
44                 {
45                     Interlocked.CompareExchange<ManualResetEvent>(ref this.asynWaitHandle, new ManualResetEvent(false), null);
46                 }
47                 return asynWaitHandle;
48             }
49         }
50         public bool CompletedSynchronously
51         {
52             get { return completedSynchronously; }
53         }
54         public bool IsCompleted
55         {
56             get { return isCompleted; }
57         }
58 
59         public void Work()
60         {
61             //do someing
62             Thread.Sleep(3000); ;
63             Result = "The Silent Southern Girl";
64             asyncState = this;
65             completedSynchronously = false;
66             isCompleted = true;
67             asynWaitHandle.Set();
68         }
69 
70     }
71 
72     public class AsyncWorkTest
73     {
74         public IAsyncResult BeginWork(AsyncCallback callback, object state)
75         {
76             AsyncResult result = new AsyncResult();
77             ThreadPool.QueueUserWorkItem((action) =>
78             {
79                 result.Work();
80                 if (callback != null)
81                 {
82                     callback((AsyncResult)state);
83                 }
84             }, state);
85             return result;
86         }
87 
88         public string EndWork(IAsyncResult re)
89         {
90             AsyncResult result = (AsyncResult)re;
91             result.AsyncWaitHandle.WaitOne();
92             return result.Result;
93         }
94     }
95 
96 }

View Code