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

Definición

Obtiene WaitHandle que se utiliza para esperar a que finalice una operación asincrónica.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

Valor de propiedad

WaitHandle que se utiliza para esperar a que finalice una operación asincrónica.A WaitHandle that is used to wait for an asynchronous operation to complete.

Ejemplos

En el ejemplo siguiente se muestra cómo usar AsyncWaitHandle la propiedad para obtener WaitHandleun y 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 al que se llama de forma asincrónica y la clase que Main contiene el método que realiza la llamada.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.

Para obtener más información y ejemplos de cómo llamar a métodos de forma asincrónica mediante delegados, consulte llamar a métodos sincrónicos de forma asincrónica.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.".

Comentarios

El valor devuelto permite al cliente esperar a que se complete una operación asincrónica en lugar de sondear IsCompleted hasta que finalice la operación.The return value allows the client to wait for an asynchronous operation to complete instead of polling IsCompleted until the operation concludes. El valor devuelto se puede utilizar para realizar WaitOneuna WaitAnyoperación, WaitAll o.The return value can be used to perform a WaitOne, WaitAny, or WaitAll operation.

El Common Language Runtime proporciona una serie de objetos que se van a esperar ManualResetEvent, AutoResetEventcomo, Mutexy, todos los que reflejan primitivas de sincronización de Win32.The common language runtime supplies a number of waitable objects, such as ManualResetEvent, AutoResetEvent, and Mutex, all of which mirror Win32 synchronization primitives.

Notas a los implementadores

El objeto que implementa IAsyncResult no necesita WaitHandle crear hasta que se lea la AsyncWaitHandle propiedad.The object that implements IAsyncResult does not need to create the WaitHandle until the AsyncWaitHandle property is read. Es la opción del IAsyncResult implementador.It is the choice of the IAsyncResult implementer. Sin embargo, si el implementador AsyncWaitHandlecrea, es responsabilidad del implementador señalar el WaitHandle que finalizará la espera en el momento adecuado.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. Por ejemplo, AsyncResult finaliza la espera en nombre del llamador cuando un método invocado de forma asincrónica devuelve.For example, AsyncResult terminates the wait on behalf of the caller when an asynchronously invoked method returns. Una vez creado AsyncWaitHandle , debe mantenerse activo hasta que el usuario llame al método que concluye la operación asincrónica.Once created, AsyncWaitHandle should be kept alive until the user calls the method that concludes the asynchronous operation. En ese momento, se puede AsyncWaitHandle descartar el objeto subyacente.At that time the object behind AsyncWaitHandle can be discarded.

Notas a los autores de las llamadas

Los clientes que esperan a que se complete la operación (en contraposición al sondeo) utilizan esta propiedad para obtener un objeto de sincronización en el que esperar.Clients that wait for the operation to complete (as opposed to polling) use this property to obtain a synchronization object to wait on.


Cuando se usa el BeginInvoke método de un delegado para llamar a un método de forma asincrónica y obtener un identificador de IAsyncResultespera del resultado, se recomienda que cierre el identificador de espera en cuanto termine de usarlo, llamando al Close() método.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 simplemente libera todas las referencias al identificador de espera, se liberan los recursos del sistema cuando la recolección de elementos no utilizados reclama el identificador de espera, pero la recolección de elementos no utilizados funciona más eficazmente cuando los objetos descartables se cierran o eliminan explícitamente.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. Para obtener más información, vea la propiedad AsyncWaitHandle.For more information, see the AsyncWaitHandle property.

Se aplica a