AsyncResult.AsyncWaitHandle AsyncResult.AsyncWaitHandle AsyncResult.AsyncWaitHandle AsyncResult.AsyncWaitHandle Property

Definition

Ruft ein WaitHandle ab, das Win32-Synchronisierungshandles kapselt und die Implementierung verschiedener Synchronisierungsschemas ermöglicht.Gets a WaitHandle that encapsulates Win32 synchronization handles, and allows the implementation of various synchronization schemes.

public:
 virtual property System::Threading::WaitHandle ^ AsyncWaitHandle { System::Threading::WaitHandle ^ get(); };
public virtual System.Threading.WaitHandle AsyncWaitHandle { get; }
member this.AsyncWaitHandle : System.Threading.WaitHandle
Public Overridable ReadOnly Property AsyncWaitHandle As WaitHandle

Eigenschaftswert

Ein WaitHandle, das Win32-Synchronisierungshandles kapselt und die Implementierung verschiedener Synchronisierungsschemas ermöglicht.A WaitHandle that encapsulates Win32 synchronization handles, and allows the implementation of various synchronization schemes.

Implementiert

Beispiele

Im folgenden Beispiel wird veranschaulicht, wie die AsyncWaitHandle -Eigenschaft zum Abrufen WaitHandleeines-Objekts und zum warten auf einen asynchronen Aufruf eines Delegaten verwendet wird.The following example demonstrates how to use the AsyncWaitHandle property to get a WaitHandle, and how to wait for an asynchronous call on a delegate. Das WaitHandle wird bei Beendigung des asynchronen Aufrufs signalisiert, und durch Aufrufen der WaitOne -Methode kann darauf gewartet werden.The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.

Das Beispiel besteht aus zwei Klassen, der-Klasse, die die Methode enthält, die asynchron aufgerufen wird, und der- Main Klasse, die die Methode enthält, die den Aufruf durchführt.The example consists of two classes, the class that contains the method which is called asynchronously, and the class that contains the Main method that makes the call.

Weitere Informationen und weitere Beispiele zum asynchronen Aufrufen von Methoden mithilfe von Delegaten finden Sie unter Asynchrones Aufrufen synchroner Methoden.For more information and more examples of calling methods asynchronously by using delegates, see Calling Synchronous Methods Asynchronously.

using namespace System;
using namespace System::Threading;
using namespace System::Runtime::InteropServices; 

namespace Examples {
namespace AdvancedProgramming {
namespace AsynchronousOperations
{
    public ref class AsyncDemo 
    {
    public:
        // The method to be executed asynchronously.
        String^ TestMethod(int callDuration, [OutAttribute] int% threadId) 
        {
            Console::WriteLine("Test method begins.");
            Thread::Sleep(callDuration);
            threadId = Thread::CurrentThread->ManagedThreadId;
            return String::Format("My call time was {0}.", callDuration);
        }
    };

    // The delegate must have the same signature as the method
    // it will call asynchronously.
    public delegate String^ AsyncMethodCaller(int callDuration, [OutAttribute] int% threadId);
}}}
using System;
using System.Threading; 

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncDemo 
    {
        // The method to be executed asynchronously.
        public string TestMethod(int callDuration, out int threadId) 
        {
            Console.WriteLine("Test method begins.");
            Thread.Sleep(callDuration);
            threadId = Thread.CurrentThread.ManagedThreadId;
            return String.Format("My call time was {0}.", callDuration.ToString());
        }
    }
    // The delegate must have the same signature as the method
    // it will call asynchronously.
    public delegate string AsyncMethodCaller(int callDuration, out int threadId);
}
Imports System.Threading
Imports System.Runtime.InteropServices 

Namespace Examples.AdvancedProgramming.AsynchronousOperations
    Public Class AsyncDemo 
        ' The method to be executed asynchronously.
        Public Function TestMethod(ByVal callDuration As Integer, _
                <Out> ByRef threadId As Integer) As String
            Console.WriteLine("Test method begins.")
            Thread.Sleep(callDuration)
            threadId = Thread.CurrentThread.ManagedThreadId()
            return String.Format("My call time was {0}.", callDuration.ToString())
        End Function
    End Class

    ' The delegate must have the same signature as the method
    ' it will call asynchronously.
    Public Delegate Function AsyncMethodCaller(ByVal callDuration As Integer, _
        <Out> ByRef threadId As Integer) As String
End Namespace
#using <TestMethod.dll>

using namespace System;
using namespace System::Threading;
using namespace Examples::AdvancedProgramming::AsynchronousOperations;

void main() 
{
    // The asynchronous method puts the thread id here.
    int threadId;

    // Create an instance of the test class.
    AsyncDemo^ ad = gcnew AsyncDemo();

    // Create the delegate.
    AsyncMethodCaller^ caller = gcnew AsyncMethodCaller(ad, &AsyncDemo::TestMethod);
       
    // Initiate the asychronous call.
    IAsyncResult^ result = caller->BeginInvoke(3000, 
        threadId, nullptr, nullptr);

    Thread::Sleep(0);
    Console::WriteLine("Main thread {0} does some work.",
        Thread::CurrentThread->ManagedThreadId);

    // Wait for the WaitHandle to become signaled.
    result->AsyncWaitHandle->WaitOne();

    // Perform additional processing here.
    // Call EndInvoke to retrieve the results.
    String^ returnValue = caller->EndInvoke(threadId, result);

    // Close the wait handle.
    result->AsyncWaitHandle->Close();

    Console::WriteLine("The call executed on thread {0}, with return value \"{1}\".",
        threadId, returnValue);
}

/* This example produces output similar to the following:

Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
 */
using System;
using System.Threading;

namespace Examples.AdvancedProgramming.AsynchronousOperations
{
    public class AsyncMain 
    {
        static void Main() 
        {
            // The asynchronous method puts the thread id here.
            int threadId;

            // Create an instance of the test class.
            AsyncDemo ad = new AsyncDemo();

            // Create the delegate.
            AsyncMethodCaller caller = new AsyncMethodCaller(ad.TestMethod);
       
            // Initiate the asychronous call.
            IAsyncResult result = caller.BeginInvoke(3000, 
                out threadId, null, null);

            Thread.Sleep(0);
            Console.WriteLine("Main thread {0} does some work.",
                Thread.CurrentThread.ManagedThreadId);

            // Wait for the WaitHandle to become signaled.
            result.AsyncWaitHandle.WaitOne();

            // Perform additional processing here.
            // Call EndInvoke to retrieve the results.
            string returnValue = caller.EndInvoke(out threadId, result);

            // Close the wait handle.
            result.AsyncWaitHandle.Close();

            Console.WriteLine("The call executed on thread {0}, with return value \"{1}\".",
                threadId, returnValue);
        }
    }
}

/* This example produces output similar to the following:

Main thread 1 does some work.
Test method begins.
The call executed on thread 3, with return value "My call time was 3000.".
 */
Imports System.Threading
Imports System.Runtime.InteropServices 

Namespace Examples.AdvancedProgramming.AsynchronousOperations

    Public Class AsyncMain 
        Shared Sub Main() 
            ' The asynchronous method puts the thread id here.
            Dim threadId As Integer

            ' Create an instance of the test class.
            Dim ad As New AsyncDemo()

            ' Create the delegate.
            Dim caller As New AsyncMethodCaller(AddressOf ad.TestMethod)
       
            ' Initiate the asynchronous call.
            Dim result As IAsyncResult = caller.BeginInvoke(3000, _
                threadId, Nothing, Nothing)

            Thread.Sleep(0)
            Console.WriteLine("Main thread {0} does some work.", _
                Thread.CurrentThread.ManagedThreadId)
            ' Perform additional processing here and then
            ' wait for the WaitHandle to be signaled.
            result.AsyncWaitHandle.WaitOne()

            ' Call EndInvoke to retrieve the results.
            Dim returnValue As String = caller.EndInvoke(threadId, result)

            ' Close the wait handle.
            result.AsyncWaitHandle.Close()

            Console.WriteLine("The call executed on thread {0}, with return value ""{1}"".", _
                threadId, returnValue)
        End Sub
    End Class
End Namespace

'This example produces output similar to the following:
'
'Main thread 1 does some work.
'Test method begins.
'The call executed on thread 3, with return value "My call time was 3000.".

Hinweise

Der WaitHandle , der von dieser Methode zurückgegeben wird, wird automatisch signalisiert, wenn der asynchrone Vorgang abgeschlossen wurde.The WaitHandle returned by this method is automatically signaled when the asynchronous operation has completed.

Das Wait-Handle wird nicht automatisch geschlossen, wenn EndInvoke Sie für den Delegaten aufzurufen, der zum Ausführen des asynchronen Methoden Aufrufes verwendet wurde.The wait handle is not closed automatically when you call EndInvoke on the delegate that was used to make the asynchronous method call. Wenn Sie alle Verweise auf das Wait-Handle freigeben, werden Systemressourcen frei, sobald das Wait-Handle von der Garbage Collection zurückgefordert wird.If you release all references to the wait handle, system resources are freed when garbage collection reclaims the wait handle. Um die Systemressourcen freizugeben, sobald die Verwendung des Wait-Handles abgeschlossen ist, müssen WaitHandle.Close Sie die-Methode aufzurufen.To free the system resources as soon as you are finished using the wait handle, call the WaitHandle.Close method. Die Garbage Collection funktioniert effizienter, wenn verwerfbare Objekte explizit geschlossen oder verworfen werden.Garbage collection works more efficiently when disposable objects are explicitly closed or disposed.

Achtung

Der WaitHandle , der in AsyncWaitHandle der-Eigenschaft enthalten ist, kann zum Blockieren des aktuellen Threads verwendet werden, bis der asynchrone-Befehl abgeschlossen ist.The WaitHandle contained in the AsyncWaitHandle property can be used to block the current thread until the asynchronous call is complete. Der WaitHandle ignoriert jedoch das AsyncCallback, wenn während des BeginInvoke Aufrufes angegeben wurde.However the WaitHandle will ignore the AsyncCallback, if one was specified during the BeginInvoke call. Daher kann es vorkommen, dass die Anwendung heruntergefahren wird, bevor AsyncCallback die Ausführung von abgeschlossen ist. Dies gilt auch dann, wenn eine WaitHandle zum Blockieren bis zum Abschluss des asynchronen Aufrufens verwendet wird.Therefore, a situation can occur where the application shuts down before the AsyncCallback has finished executing, even if a WaitHandle is used to block until the asynchronous call completion. Ein Beispiel für eine solche Situation finden Sie im Beispiel für die AsyncResult -Klasse, und entfernen Sie die Thread.Sleep -Anweisung.For an example of such a situation, see the example for the AsyncResult class, and remove the Thread.Sleep statement.

Gilt für:

Siehe auch