IAsyncResult.IsCompleted Proprietà

Definizione

Ottiene un valore che indica l'eventuale completamento dell'operazione asincrona.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

Valore della proprietà

Boolean

true se l'operazione viene completata. In caso contrario, false.true if the operation is complete; otherwise, false.

Esempio

Nell'esempio seguente viene illustrato come utilizzare la IsCompleted proprietà dell'oggetto IAsyncResult per individuare quando viene completata una chiamata asincrona.The following example shows how to use the IsCompleted property of the IAsyncResult to discover when an asynchronous call completes. In questo caso, la chiamata asincrona viene eseguita utilizzando il BeginInvoke metodo di un delegato.In this case, the asynchronous call is made by using the BeginInvoke method of a delegate. È possibile usare la IsCompleted proprietà per eseguire il polling del completamento quando si effettua la chiamata asincrona da un thread che servizi l'interfaccia utente.You might use the IsCompleted property to poll for completion when making the asynchronous call from a thread that services the user interface. Il polling del completamento consente al thread chiamante di continuare l'esecuzione mentre viene eseguita la chiamata asincrona su un thread ThreadPool .Polling for completion allows the calling thread to continue executing while the asynchronous call executes on a ThreadPool thread.

L'esempio è costituito da due classi: la classe che contiene il metodo chiamato in modo asincrono e la classe che contiene il Main metodo che effettua la chiamata.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.

Per ulteriori informazioni ed esempi relativi alla chiamata asincrona dei metodi mediante l'utilizzo di delegati, vedere chiamata asincrona dei metodi sincroni.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.".

Commenti

Quando questa proprietà è true , è possibile presupporre che sia possibile rimuovere tutte le risorse allocate per l'utilizzo da parte dell'operazione asincrona.When this property is true, you can assume it is safe to discard any resources you allocate for use by the asynchronous operation.

Note per gli implementatori

Gli implementatori restituiranno in genere il valore di un campo privato o di un test interno come valore di questa proprietà.Implementers will typically return the value of a private field or internal test as the value of this property.

Note per i chiamanti

I client che eseguono il polling dello stato dell'operazione (in contrapposizione all'attesa di un oggetto di sincronizzazione) utilizzano questa proprietà per determinare lo stato dell'operazione.Clients that poll for operation status (as opposed to waiting on a synchronization object) use this property to determine the status of the operation.

Si applica a