IAsyncResult.AsyncWaitHandle Propriété

Définition

Obtient un WaitHandle qui est utilisé pour attendre qu’une opération asynchrone se termine.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

Valeur de propriété

WaitHandle utilisé pour attendre qu’une opération asynchrone se termine.A WaitHandle that is used to wait for an asynchronous operation to complete.

Exemples

L’exemple suivant montre comment utiliser la propriété AsyncWaitHandle pour obtenir un WaitHandle, et comment attendre un appel asynchrone sur un délégué.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. Le WaitHandle est signalé quand l’appel asynchrone se termine et vous pouvez l’attendre en appelant la méthode WaitOne .The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.

L’exemple se compose de deux classes : la classe qui contient la méthode qui est appelée de façon asynchrone et la classe qui contient la méthode Main qui effectue l’appel.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.

Pour plus d’informations et pour obtenir d’autres exemples d’appel de méthodes de façon asynchrone à l’aide de délégués, consultez appel de méthodes synchrones de façon asynchrone.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.".

Remarques

La valeur de retour permet au client d’attendre qu’une opération asynchrone se termine au lieu d’interroger IsCompleted jusqu’à ce que l’opération se termine.The return value allows the client to wait for an asynchronous operation to complete instead of polling IsCompleted until the operation concludes. La valeur de retour peut être utilisée pour effectuer une opération WaitOne, WaitAnyou WaitAll.The return value can be used to perform a WaitOne, WaitAny, or WaitAll operation.

Le common language runtime fournit un certain nombre d’objets pouvant être attendus, tels que ManualResetEvent, AutoResetEventet Mutex, qui reflètent tous les primitives de synchronisation Win32.The common language runtime supplies a number of waitable objects, such as ManualResetEvent, AutoResetEvent, and Mutex, all of which mirror Win32 synchronization primitives.

Notes pour les responsables de l’implémentation

L’objet qui implémente IAsyncResult n’a pas besoin de créer le WaitHandle tant que la propriété AsyncWaitHandle n’est pas lue.The object that implements IAsyncResult does not need to create the WaitHandle until the AsyncWaitHandle property is read. C’est le choix de l’implémenteur IAsyncResult.It is the choice of the IAsyncResult implementer. Toutefois, si l’implémenteur crée AsyncWaitHandle, il est de la responsabilité de l’implémenteur de signaler le WaitHandle qui met fin à l’attente au moment opportun.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. Par exemple, AsyncResult met fin à l’attente pour le compte de l’appelant lorsqu’une méthode appelée de manière asynchrone retourne.For example, AsyncResult terminates the wait on behalf of the caller when an asynchronously invoked method returns. Une fois créé, AsyncWaitHandle doit rester actif jusqu’à ce que l’utilisateur appelle la méthode qui termine l’opération asynchrone.Once created, AsyncWaitHandle should be kept alive until the user calls the method that concludes the asynchronous operation. À ce moment-là, l’objet sous-jacent AsyncWaitHandle peut être ignoré.At that time the object behind AsyncWaitHandle can be discarded.

Notes pour les appelants

Les clients qui attendent que l’opération se termine (par opposition à l’interrogation) utilisent cette propriété pour obtenir un objet de synchronisation à attendre.Clients that wait for the operation to complete (as opposed to polling) use this property to obtain a synchronization object to wait on.


Quand vous utilisez la méthode BeginInvoke d’un délégué pour appeler une méthode de façon asynchrone et obtenir un handle d’attente à partir du IAsyncResultrésultant, nous vous recommandons de fermer le handle d’attente dès que vous en avez terminé avec l’appel de la méthode Close().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. Si vous publiez simplement toutes les références au handle d’attente, les ressources système sont libérées lorsque garbage collection récupère le handle d’attente, mais garbage collection fonctionne plus efficacement quand les objets jetables sont explicitement fermés ou supprimés.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. Pour plus d'informations, consultez la propriété AsyncWaitHandle.For more information, see the AsyncWaitHandle property.

S’applique à