簡要介紹：
1.定義非同步執行需要呼叫的方法
2.定義具有與非同步執行方法相同簽名的委託(Delegate)；
3.呼叫 BeginInvoke 和 EndInvoke 方法。
   3.1. BeginInvoke 方法用於啟動非同步呼叫。它與需要非同步執行的方法具有相同的引數，
       只不過還有兩個額外的引數。BeginInvoke 立即返回，不等待非同步呼叫完成。
       BeginInvoke 返回 IasyncResult，可用於監視呼叫進度。
   3.2. EndInvoke 方法用於檢索非同步呼叫結果。呼叫 BeginInvoke 後可隨時呼叫 EndInvoke 方法；
       如果非同步呼叫未完成，EndInvoke 將一直阻塞到非同步呼叫完成。
       EndInvoke 的引數包括需要非同步執行的方法的 out 和 ref 引數以及由 BeginInvoke 返回的 IAsyncResult。
   3.3.呼叫了 BeginInvoke 後，可以：
      * 進行某些操作，然後呼叫 EndInvoke 一直阻塞到呼叫完成。
      * 使用 IAsyncResult.AsyncWaitHandle 獲取 WaitHandle，使用它的 WaitOne 方法將執行一直阻塞到發出 WaitHandle 訊號，然後呼叫 EndInvoke。
      * 輪詢由 BeginInvoke 返回的 IAsyncResult，確定非同步呼叫何時完成，然後呼叫 EndInvoke。
      * 將用於回撥方法的委託傳遞給 BeginInvoke。該方法在非同步呼叫完成後在 ThreadPool 執行緒上執行，它可以呼叫 EndInvoke。  


//具體程式碼如下:

using System;
using System.Threading;

//The example of using delegate
namespace DelegateCallAsynchronousMethods
{

    class AsyncFileDelegate
   {
       /*
        *這是需要非同步執行的方法，COPY一個檔案
        */

        public void CopyFile(String fileName, out bool result)
        {
            Console.WriteLine("Move file "+fileName+"...");
            for (int i = 0; i < 10; i++)
            {
                Thread.Sleep(200);
                Console.WriteLine("Move file is running..." + i);
            }
            Console.WriteLine("Move file finished");
            result = true;
        }
       
       /*
        *定義COPY檔案的委託，將來CopyFile方法就委託給它去非同步執行
        */

        public delegate void CopyFileDelegate(String fileName, out bool result);//Declare copy file delegate

        static void Main()
       {
            bool result;
            AsyncFileDelegate aa = new AsyncFileDelegate();
            // 開始委託方法，以後都由copyFile這個變數來做事
            CopyFileDelegate copyFile = new CopyFileDelegate(aa.CopyFile);

            Console.WriteLine("[Main] Invoking the asynchronous "+" Copy file method");
            //委託呼叫非同步方法去執行

            IAsyncResult iAR = copyFile.BeginInvoke("songlin.txt", out result, null, null);

            // 主方法不用等待COPY FILE方法，繼續自己的事情
            Console.WriteLine("[Main] Doing other work");
            for (int i = 0; i < 10; i++)
           {
                Thread.Sleep(200);
                Console.WriteLine("[Main]MainMethod is running..."+i);
            }
           
           
            Console.WriteLine(" [Main] Waiting for file transformation to finish");
            /* 主方法自己的事情做完，開始檢查COPYFILE有沒有完成。
             * 使用它的 WaitOne 方法將執行一直等到發出 WaitHandle 訊號，然後呼叫 EndInvoke。
             * 注意：非同步呼叫完成時會發出 WaitHandle 訊號，可以通過WaitOne 來等待它*/
            iAR.AsyncWaitHandle.WaitOne();

            Console.WriteLine("[Main] Copy file finished, cleaning up");
            /* EndInvoke 方法用於檢索非同步呼叫結果。呼叫 BeginInvoke 後可隨時呼叫 EndInvoke 方法；
             * 如果非同步呼叫未完成，EndInvoke 將一直阻塞到非同步呼叫完成。
             */
            copyFile.EndInvoke(out result, iAR);

            Console.WriteLine("[Main] The result is {0}", result);
            Console.ReadLine();
        }
    };

}

下面是輸出結果，可以看出copyfile方法和主方法是非同步執行的。
----------------------------------------------------------------------------------------------
[Main] Invoking the asynchronous Copy file method
[Main] Doing other work
Move file songlin.txt...
[Main]MainMethod is running...0
Move file is running...0
[Main]MainMethod is running...1
Move file is running...1
[Main]MainMethod is running...2
Move file is running...2
[Main]MainMethod is running...3
Move file is running...3
[Main]MainMethod is running...4
Move file is running...4
[Main]MainMethod is running...5
Move file is running...5
[Main]MainMethod is running...6
Move file is running...6
[Main]MainMethod is running...7
Move file is running...7
[Main]MainMethod is running...8
Move file is running...8
[Main]MainMethod is running...9
[Main] Waiting for file transformation to finish
Move file is running...9
Move file finished
[Main] Copy file finished, cleaning up
[Main] The result is True

以下是程式碼例子，模擬了檔案拷貝。每個檔案的拷貝方法都是在非同步方式下執行，同時主方法依然執行。

在主方法的最後會等待直到所有的非同步方法執行完成。

namespace WindowsApplication2

{

public class AsyncFileCopy

{

//Declare copy file delegate, will use this to invoke real copy file method

publicdelegate string CopyFileDelegate(int fileSize);

//The real file copy method, we simulate file copy with thread sleep

public String CopyFile(int fileSize)

{

switch (fileSize)

{

case 1:

Console.WriteLine("File 1 copy start...");

Thread.Sleep(1000);

Console.WriteLine("File 1 copy finished");

return "One";

case 2:

Console.WriteLine("File 2 copy Start...");

Thread.Sleep(2000);

Console.WriteLine("File 2 copy Finished");

return "Two";

case 3:

Console.WriteLine("File 3 copyStart...");

Thread.Sleep(3000);

Console.WriteLine("File 3 copy Finished");

return "Three";

default:

return "default";

}

}

public void ExecuteCopy()

{

List<WaitHandle> list = new List<WaitHandle>();

Console.WriteLine("Main method Start");

//Init coyp file delegate

CopyFileDelegate dlg = new CopyFileDelegate(CopyFile);

//Assume we have 4 different size files.

//Section below will let each file be copied in Async model

for (int i = 0; i < 4; i++)

{

//Let copy file executed in Async model, main thread continue

IAsyncResult ar = dlg.BeginInvoke(i, null, null);

list.Add(ar.AsyncWaitHandle);

Console.WriteLine("Main method still working" + i);

Thread.Sleep(10);//simulate main method cost some time

}

//Ensure all Async method finished before return from main method

System.Threading.WaitHandle.WaitAll(list.ToArray());

Console.WriteLine("Main method finished");

}

public static void <?XML:NAMESPACE PREFIX = ST1 />Main(string[] args)

{

AsyncFileCopy test = new AsyncFileCopy();

test.ExecuteCopy();

}

}

}