IAsyncResult.IsCompleted Properti

Definisi

Ruang nama:

System

Rakitan:

netstandard.dll, System.Runtime.dll

Sumber:

IAsyncResult.cs

Mendapatkan nilai yang menunjukkan apakah operasi asinkron telah selesai.

public:
 property bool IsCompleted { bool get(); };

public bool IsCompleted { get; }

member this.IsCompleted : bool

Public ReadOnly Property IsCompleted As Boolean

Nilai Properti

Boolean

true jika operasi selesai; jika tidak, false.

Contoh

Contoh berikut menunjukkan cara menggunakan IsCompleted properti untuk IAsyncResult menemukan saat panggilan asinkron selesai. Dalam hal ini, panggilan asinkron dilakukan dengan menggunakan BeginInvoke metode delegasi. Anda dapat menggunakan IsCompleted properti untuk melakukan polling untuk penyelesaian saat melakukan panggilan asinkron dari utas yang melayani antarmuka pengguna. Polling untuk proses penyelesaian memungkinkan utas pemanggil untuk tetap melanjutkan eksekusi saat panggilan asinkron dijalankan pada utas ThreadPool.

Contohnya terdiri dari dua kelas: kelas yang berisi metode yang disebut secara asinkron, dan kelas yang berisi Main metode yang melakukan panggilan.

Untuk informasi selengkapnya dan contoh selengkapnya tentang metode panggilan secara asinkron dengan menggunakan delegasi, lihat Memanggil Metode Sinkron Secara Asinkron.

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 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) {
                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.".

Keterangan

Ketika properti ini adalah true, Anda dapat berasumsi aman untuk membuang sumber daya apa pun yang Anda alokasikan untuk digunakan oleh operasi asinkron.

Catatan Bagi Implementer

Pelaksana biasanya akan mengembalikan nilai bidang privat atau pengujian internal sebagai nilai properti ini.

Catatan Bagi Pemanggil

Klien yang melakukan polling untuk status operasi (dibandingkan dengan menunggu objek sinkronisasi) menggunakan properti ini untuk menentukan status operasi.