Asynchronously ????? C# ?????? ?? ??? ???? ?? ??? ???? ????

??????????

• Microsoft Windows 2000 ?? Microsoft Windows XP ?? Microsoft Windows Server 2003
• ????? Studio .NET ?? Visual Studio 2005

• ?????? ??????? ??? ????? C#
• ???????????? ?? ????? ???? ????

?????????? ??? ????? ???? ????

// The following delegate 
delegate string MethodDelegate(int iCallTime, out int iExecThread)  ;

// will have the following BeginInvoke() and EndInvoke methods:
IAsyncResult MethodDelegate.BeginInvoke(int iCallTime, out int iExecThread, AsyncCallback cb, object AsyncState); 

string MethodDelegate.EndInvoke (out int iExecThread, IAsyncResult ar) ;
				

• ???????? ??? ?? ??? ????? ???? ??? ?? ??? ?? ????? ????EndInvoke().
• ??????? ???WaitHandle?????? ???? ??? ??IAsyncResult????????, ?? ????? ????WaitOne?? ?? ??????? ???? ?? ??? ????WaitHandle?????? ??, ?? ???? ??? ???EndInvoke().
• PollIAsyncResult?? ?????????? ??? ????? ?? ???? ?? ?? ????????? ???? ?? ??? ????????, ?? ???? ??? ???EndInvoke().
• ???? ?????? ????????? ?????? ??????? ??? ?????? ??? ?? ?????? ??????? ???EndInvoke()?? ??????????? ?????????? ??? ???? ???? ?? ??? ???? ?? ?????? ???

string LongRunningMethod (int iCallTime, out int iExecThread)
{
	Thread.Sleep (iCallTime) ;
	iExecThread = AppDomain.GetCurrentThreadId ();
	return "MyCallTime was " + iCallTime.ToString() ;
}

				

delegate string MethodDelegate(int iCallTime, out int iExecThread)  ;
				

????? 1: ??? ??? ???? Synchronously

1. Microsoft Visual Studio .NET ?? Microsoft Visual Studio 2005 ??????? ?????
2. ??? ??? ????? C# ????? ????????? ????????? AsyncDemo ??? ??????
3. ????????? ??? ??? ?? .cs ????? ?? ??? ?? ??? ??? ???????? AsyncDemo ??? ?? ?? ????? ??????:

   using System;
   using System.Threading ; 
   using System.Windows.Forms ;
   
   public class AsyncDemo
   {
   	string LongRunningMethod (int iCallTime, out int iExecThread)
   	{
   		Thread.Sleep (iCallTime) ;
   		iExecThread = AppDomain.GetCurrentThreadId ();
   		return "MyCallTime was " + iCallTime.ToString() ;
   	}
   
   	delegate string MethodDelegate(int iCallTime, out int iExecThread)  ;
   
   	public void DemoSyncCall()
   	{
   		string s ;
   		int iExecThread;
   
   		// Create an instance of a delegate that wraps LongRunningMethod.
   		MethodDelegate dlgt = new MethodDelegate (this.LongRunningMethod) ;  
   			
   		// Call LongRunningMethod using the delegate.
   		s = dlgt(3000, out iExecThread);  
   			
   		MessageBox.Show (string.Format ("The delegate call returned the string:   \"{0}\", 
                                           and the thread ID {1}", s, iExecThread.ToString() ) );
   	}
   }
   					

   ????????? ???? ?? ??? ???, ?? ???? ?? ?????????? ??? ???? ?? ??? ???? ????? ???????? ????, ??? ??, ???? ?????DemoSyncCall()????, ?? synchronously ????????? ?? ??? ???? ?? ??? ???? ????????? ???? ?? ???
4. ?? ????? ??? ??? ????? ??? ????????????????? ?? ???? ????????? ??? Visual Studio ???? ?? ????? ??:

   static void Main(string[] args)
   {
   	AsyncDemo ad = new AsyncDemo () ;
   	ad.DemoSyncCall() ;
   }
   					

5. ???? ????????? ?? ????? ?? ??? CTRL + F5 ??????

????? 2: ??? ??? ???? Asynchronously ?? ????? ??EndInvoke()???????? ?? ??? ????

1. Add a method namedDemoEndInvoke()???? ?? ???AsyncDemo????? TheDemoEndInvokefunction demonstrates how to call the delegate asynchronously.

   public void DemoEndInvoke()
   {
   	MethodDelegate dlgt = new MethodDelegate (this.LongRunningMethod) ;
   	string s ;
   	int iExecThread;
   
   	// Initiate the asynchronous call.
   	IAsyncResult ar = dlgt.BeginInvoke(3000, out iExecThread, null, null);  
   
   	// Do some useful work here. This would be work you want to have
   	// run at the same time as the asynchronous call.
   
   	// Retrieve the results of the asynchronous call.
   	s = dlgt.EndInvoke (out iExecThread, ar) ;  
   
   	MessageBox.Show (string.Format ("The delegate call returned the string:   \"{0}\", 
                                  and the number {1}", s, iExecThread.ToString() ) );
   }
   					

2. Edit the source code for?????so that it contains the following code:

   static void Main(string[] args)
   {
   	AsyncDemo ad = new AsyncDemo () ;
   	ad.DemoEndInvoke() ;
   }
   					

3. Press CTRL+F5 to run your application.

Sample 3: Calling A Method Asynchronously And Using A WaitHandle To Wait For The Call To Complete

1. Add a function namedDemoWaitHandle()???? ?? ???AsyncDemo????? TheDemoWaitHandle()function demonstrates how to call the delegate asynchronously.

   public void DemoWaitHandle ()
   {
   	string s ;
   	int iExecThread;
   
   	MethodDelegate dlgt = new MethodDelegate (this.LongRunningMethod) ;
   
   	// Initiate the asynchronous call.
   	IAsyncResult ar = dlgt.BeginInvoke(3000, out iExecThread, null, null); 
   
   	// Do some useful work here. This would be work you want to have
   	// run at the same time as the asynchronous call.
   
   	// Wait for the WaitHandle to become signaled.
   	ar.AsyncWaitHandle.WaitOne() ;
   
   	// Get the results of the asynchronous call.
   	s = dlgt.EndInvoke (out iExecThread, ar) ;
   			
   	MessageBox.Show (string.Format ("The delegate call returned the string:   \"{0}\", 
                                    and the number {1}", s, iExecThread.ToString() ) );
   }
   					

2. Edit the source code for?????so that it contains the following code:

   static void Main(string[] args)
   {
   	AsyncDemo ad = new AsyncDemo () ;
   	ad.DemoWaitHandle () ;
   }
   					

3. Press CTRL+F5 to run your application.

Sample 4: Calling A Method Asynchronously by Using the Polling Call Pattern

1. Add a function namedDemoPolling()???? ?? ???AsyncDemo????? TheDemoPolling()function demonstrates how to call the delegate asynchronously and use polling to see if the process is complete.

   public void DemoPolling()
   {
   	MethodDelegate dlgt = new MethodDelegate (this.LongRunningMethod) ;
   	string s ;
   	int iExecThread;
   
   	// Initiate the asynchronous call.
   	IAsyncResult ar = dlgt.BeginInvoke(3000, out iExecThread, null, null); 
   
   	// Poll IAsyncResult.IsCompleted
   	while(ar.IsCompleted == false)
   	{
   		Thread.Sleep (10) ;  // pretend to so some useful work
   	}
   	s = dlgt.EndInvoke (out iExecThread, ar) ;
   
   	MessageBox.Show (string.Format ("The delegate call returned the string:   \"{0}\", 
                                   and the number {1}", s, iExecThread.ToString() ) );
   }
   
   					

2. Edit the source code for?????. Replace the content of the function with the following code:

   static void Main(string[] args)
   {
   	AsyncDemo ad = new AsyncDemo () ;
   	ad.DemoPolling () ;
   }
   					

3. ???? ????????? ?? ????? ?? ??? CTRL + F5 ??????

Sample 5: Executing a Callback When an Asynchronous Method Completes

1. Add a two methods namedDemoCallback(), ??MyAsyncCallback()???? ?? ???AsyncDemo????? TheDemoCallback()method demonstrates how to call the delegate asynchronously. It uses a delegate to wrap theMyAsyncCallback()method, which the system calls when the asynchronous operation completes.MyAsyncCallback()callsEndInvoke().

   public void DemoCallback()
   {
   	MethodDelegate dlgt = new MethodDelegate (this.LongRunningMethod) ;
   	string s ;
   	int iExecThread;
   
   	// Create the callback delegate.
   	AsyncCallback cb = new AsyncCallback(MyAsyncCallback);
   
   	// Initiate the Asynchronous call passing in the callback delegate
   	// and the delegate object used to initiate the call.
   	IAsyncResult ar = dlgt.BeginInvoke(3000, out iExecThread, cb, dlgt); 
   }
   
   public void MyAsyncCallback(IAsyncResult ar)
   {
   	string s ;
   	int iExecThread ;
   
   	// Because you passed your original delegate in the asyncState parameter
   	// of the Begin call, you can get it back here to complete the call.
   	MethodDelegate dlgt = (MethodDelegate) ar.AsyncState;
   
   	// Complete the call.
   	s = dlgt.EndInvoke (out iExecThread, ar) ;
   
   	MessageBox.Show (string.Format ("The delegate call returned the string:   \"{0}\", 
                                   and the number {1}", s, iExecThread.ToString() ) );
   }
   
   					

2. Edit the source code for?????. Replace the content of the function with the following code:

   static void Main(string[] args)
   {
   	AsyncDemo ad = new AsyncDemo () ;
   	ad.DemoCallback() ;
   }
   					

3. ???? ????????? ?? ????? ?? ??? CTRL + F5 ??????

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