IAsyncResult.IsCompleted Propriété

Définition

Obtient une valeur qui indique si l’opération asynchrone est terminée.Gets a value that indicates whether the asynchronous operation has completed.

public:
 property bool IsCompleted { bool get(); };
public bool IsCompleted { get; }
member this.IsCompleted : bool
Public ReadOnly Property IsCompleted As Boolean

Valeur de propriété

true si l’opération est terminée ; sinon, false.true if the operation is complete; otherwise, false.

Exemples

L’exemple suivant montre comment utiliser la propriété IsCompleted du IAsyncResult pour découvrir quand un appel asynchrone se termine.The following example shows how to use the IsCompleted property of the IAsyncResult to discover when an asynchronous call completes. Dans ce cas, l’appel asynchrone est effectué à l’aide de la méthode BeginInvoke d’un délégué.In this case, the asynchronous call is made by using the BeginInvoke method of a delegate. Vous pouvez utiliser la propriété IsCompleted pour demander l’achèvement de l’appel asynchrone à partir d’un thread qui service l’interface utilisateur.You might use the IsCompleted property to poll for completion when making the asynchronous call from a thread that services the user interface. L’interrogation pour connaître l’état d’avancement permet au thread appelant de continuer à s’exécuter pendant que l’appel asynchrone s’exécute sur un thread ThreadPool .Polling for completion allows the calling thread to continue executing while the asynchronous call executes on a ThreadPool thread.

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);

    // Poll while simulating work.
    while(result->IsCompleted == false)
    {
        Thread::Sleep(250);
        Console::Write(".");
    }

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

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

/* This example produces output similar to the following:

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);

            // Poll while simulating work.
            while(result.IsCompleted == false) {
                Thread.Sleep(250);
                Console.Write(".");
            }

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

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

/* This example produces output similar to the following:

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)

            ' Poll while simulating work.
            While result.IsCompleted = False
                Thread.Sleep(250)
                Console.Write(".")
            End While

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

            Console.WriteLine(vbCrLf & _
                "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:
'
'Test method begins.
'.............
'The call executed on thread 3, with return value "My call time was 3000.".

Remarques

Lorsque cette propriété est true, vous pouvez supposer qu’il est possible de supprimer sans risque les ressources que vous allouez pour une utilisation par l’opération asynchrone.When this property is true, you can assume it is safe to discard any resources you allocate for use by the asynchronous operation.

Notes pour les responsables de l’implémentation

Les implémenteurs retournent généralement la valeur d’un champ privé ou d’un test interne comme valeur de cette propriété.Implementers will typically return the value of a private field or internal test as the value of this property.

Notes pour les appelants

Les clients qui interrogent l’état de l’opération (par opposition à l’attente d’un objet de synchronisation) utilisent cette propriété pour déterminer l’état de l’opération.Clients that poll for operation status (as opposed to waiting on a synchronization object) use this property to determine the status of the operation.

S’applique à