IAsyncResult.AsyncWaitHandle IAsyncResult.AsyncWaitHandle IAsyncResult.AsyncWaitHandle IAsyncResult.AsyncWaitHandle Property

Definition

Ruft einen WaitHandle ab, der verwendet wird, um auf den Abschluss eines asynchronen Vorgangs zu warten.Gets a WaitHandle that is used to wait for an asynchronous operation to complete.

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

Eigenschaftswert

Ein WaitHandle, der verwendet wird, um auf den Abschluss eines asynchronen Vorgangs zu warten.A WaitHandle that is used to wait for an asynchronous operation to complete.

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 that 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 Rückgabewert ermöglicht es dem Client, auf den Abschluss eines asynchronen Vorgangs zu warten, IsCompleted anstatt auf den Abschluss des Vorgangs zu warten.The return value allows the client to wait for an asynchronous operation to complete instead of polling IsCompleted until the operation concludes. Der Rückgabewert kann verwendet werden, um eine WaitOne- WaitAny,- WaitAll oder-Operation auszuführen.The return value can be used to perform a WaitOne, WaitAny, or WaitAll operation.

Der Common Language Runtime stellt eine Reihe von aufnutzbaren Objekten, wie ManualResetEventz AutoResetEvent. b Mutex., und, bereit, die alle die Win32-Synchronisierungs primitiven spiegeln.The common language runtime supplies a number of waitable objects, such as ManualResetEvent, AutoResetEvent, and Mutex, all of which mirror Win32 synchronization primitives.

Hinweise für Ausführende

Das Objekt, das IAsyncResult implementiert, muss WaitHandle erst dann erstellen, wenn AsyncWaitHandle die-Eigenschaft gelesen wird.The object that implements IAsyncResult does not need to create the WaitHandle until the AsyncWaitHandle property is read. Es ist die Wahl des IAsyncResult Implementierers.It is the choice of the IAsyncResult implementer. Wenn der Implementierer jedoch erstellt AsyncWaitHandle, liegt es in der Verantwortung des Implementierers, dem WaitHandle zu signalisieren, dass den warte Vorgang zur richtigen Zeit beendet.However, if the implementer creates AsyncWaitHandle, it is the responsibility of the implementer to signal the WaitHandle that will terminate the wait at the appropriate time. Beendet beispielsweise AsyncResult den warte Vorgang im Auftrag des Aufrufers, wenn eine asynchron aufgerufene Methode zurückgibt.For example, AsyncResult terminates the wait on behalf of the caller when an asynchronously invoked method returns. Nach der Erstellung AsyncWaitHandle sollte beibehalten werden, bis der Benutzer die Methode aufruft, die den asynchronen Vorgang beendet.Once created, AsyncWaitHandle should be kept alive until the user calls the method that concludes the asynchronous operation. Zu diesem Zeitpunkt kann das Objekt AsyncWaitHandle hinter verworfen werden.At that time the object behind AsyncWaitHandle can be discarded.

Hinweise für Aufrufer

Clients, die auf den Abschluss des Vorgangs warten (im Gegensatz zum Abruf), verwenden diese Eigenschaft zum Abrufen eines Synchronisierungs Objekts, auf das gewartet werden soll.Clients that wait for the operation to complete (as opposed to polling) use this property to obtain a synchronization object to wait on.


Wenn Sie die BeginInvoke -Methode eines Delegaten verwenden, um eine Methode asynchron aufzurufen und ein Wait-Handle IAsyncResultaus der resultierenden abzurufen, empfiehlt es sich, das Wait-Handle zu schließen, sobald Sie die Verwendung abgeschlossen Close() haben, indem Sie die-Methode aufrufen.When you use the BeginInvoke method of a delegate to call a method asynchronously and obtain a wait handle from the resulting IAsyncResult, we recommend that you close the wait handle as soon as you are finished using it, by calling the Close() method. Wenn Sie einfach alle Verweise auf das Wait-Handle freigeben, werden Systemressourcen freigegeben, wenn Garbage Collection das Wait-Handle zurückgibt, aber Garbage Collection effizienter funktioniert, wenn verwerfbare Objekte explizit geschlossen oder verworfen werden.If you simply release all references to the wait handle, system resources are freed when garbage collection reclaims the wait handle, but garbage collection works more efficiently when disposable objects are explicitly closed or disposed. Weitere Informationen finden Sie in den Ausführungen zur AsyncWaitHandle-Eigenschaft.For more information, see the AsyncWaitHandle property.

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