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

Definición

Obtiene un WaitHandle que encapsula identificadores de sincronización Win32, y permite la implementación de varios esquemas de sincronización.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

Valor de propiedad

WaitHandle que encapsula identificadores de sincronización Win32, y permite la implementación de varios esquemas de sincronización.A WaitHandle that encapsulates Win32 synchronization handles, and allows the implementation of various synchronization schemes.

Implementaciones

Ejemplos

En el ejemplo siguiente se muestra cómo usar el AsyncWaitHandle propiedad va a obtener un WaitHandley cómo esperar una llamada asincrónica en un delegado.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. WaitHandle se señaliza cuando finaliza la llamada asincrónica y puede esperar a que termine llamando al método WaitOne .The WaitHandle is signaled when the asynchronous call completes, and you can wait for it by calling the WaitOne method.

El ejemplo consta de dos clases, la clase que contiene el método que se llama de forma asincrónica, y la clase que contiene el Main método que realiza la llamada.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.

Para obtener más información y más ejemplos de llamar a métodos de forma asincrónica mediante delegados, vea Calling Synchronous Methods Asynchronously.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
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
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.".

Comentarios

El WaitHandle devuelta por este método se señala automáticamente cuando se ha completado la operación asincrónica.The WaitHandle returned by this method is automatically signaled when the asynchronous operation has completed.

El identificador de espera no se cierra automáticamente cuando se llama a EndInvoke en el delegado que se usó para llamar al método asincrónico.The wait handle is not closed automatically when you call EndInvoke on the delegate that was used to make the asynchronous method call. Si libera todas las referencias al identificador de espera, se liberarán los recursos del sistema cuando la recolección de elementos no utilizados reclame el identificador de espera.If you release all references to the wait handle, system resources are freed when garbage collection reclaims the wait handle. Para liberar los recursos del sistema tan pronto como haya terminado de utilizar el identificador de espera, llame a la WaitHandle.Close método.To free the system resources as soon as you are finished using the wait handle, call the WaitHandle.Close method. Colección de elementos no utilizados funciona más eficazmente cuando los objetos descartables se cierran o eliminan de forma explícita.Garbage collection works more efficiently when disposable objects are explicitly closed or disposed.

Precaución

El WaitHandle contenidos en el AsyncWaitHandle propiedad puede utilizarse para bloquear el subproceso actual hasta que se complete la llamada asincrónica.The WaitHandle contained in the AsyncWaitHandle property can be used to block the current thread until the asynchronous call is complete. Sin embargo, el WaitHandle pasará por alto el AsyncCallback, si se especificó durante la BeginInvoke llamar.However the WaitHandle will ignore the AsyncCallback, if one was specified during the BeginInvoke call. Por lo tanto, puede ocurrir que la aplicación se cierre antes de la AsyncCallback ha terminado de ejecutarse, incluso si un WaitHandle se utiliza para bloquear hasta que complete la llamada asincrónica.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. Para obtener un ejemplo de esta situación, vea el ejemplo de la AsyncResult clase y quite el Thread.Sleep instrucción.For an example of such a situation, see the example for the AsyncResult class, and remove the Thread.Sleep statement.

Se aplica a

Consulte también: