Gemeinsames Abbrechen von Threads

Vor .NET Framework 4 bot .NET keine integrierte Möglichkeit, einen Thread kooperativ abzubrechen, nachdem er gestartet wurde. Ab .NET Framework 4 können Sie jedoch eine System.Threading.CancellationToken zum Abbrechen von Threads verwenden, genauso wie Sie sie zum Abbrechen System.Threading.Tasks.Task von Objekten oder PLINQ-Abfragen verwenden können. Obwohl die System.Threading.Thread -Klasse keine integrierte Unterstützung für Abbruchtoken bietet, können Sie ein Token an eine Threadprozedur übergeben. Dazu verwenden Sie den Thread -Konstruktor, der ein ParameterizedThreadStart -Delegat akzeptiert. Im folgenden Beispiel wird die dafür erforderliche Vorgehensweise veranschaulicht.

using System;
using System.Threading;

public class ServerClass
{
    public static void StaticMethod(object? obj)
    {
        if (obj is null)
            return;

        CancellationToken ct = (CancellationToken)obj;
        Console.WriteLine("ServerClass.StaticMethod is running on another thread.");

        // Simulate work that can be canceled.
        while (!ct.IsCancellationRequested)
        {
            Thread.SpinWait(50000);
        }
        Console.WriteLine("The worker thread has been canceled. Press any key to exit.");
        Console.ReadKey(true);
    }
}

public class Simple
{
    public static void Main()
    {
        // The Simple class controls access to the token source.
        CancellationTokenSource cts = new CancellationTokenSource();

        Console.WriteLine("Press 'C' to terminate the application...\n");
        // Allow the UI thread to capture the token source, so that it
        // can issue the cancel command.
        Thread t1 = new Thread(() =>
        {
            if (Console.ReadKey(true).KeyChar.ToString().ToUpperInvariant() == "C")
                cts.Cancel();
        });

        // ServerClass sees only the token, not the token source.
        Thread t2 = new Thread(new ParameterizedThreadStart(ServerClass.StaticMethod));
        // Start the UI thread.

        t1.Start();

        // Start the worker thread and pass it the token.
        t2.Start(cts.Token);

        t2.Join();
        cts.Dispose();
    }
}
// The example displays the following output:
//       Press 'C' to terminate the application...
//
//       ServerClass.StaticMethod is running on another thread.
//       The worker thread has been canceled. Press any key to exit.

Imports System.Threading

Public Class ServerClass
    Public Shared Sub StaticMethod(obj As Object)
        Dim ct AS CancellationToken = CType(obj, CancellationToken)
        Console.WriteLine("ServerClass.StaticMethod is running on another thread.")

        ' Simulate work that can be canceled.
        While Not ct.IsCancellationRequested
            Thread.SpinWait(50000)
        End While
        Console.WriteLine("The worker thread has been canceled. Press any key to exit.")
        Console.ReadKey(True)
    End Sub
End Class

Public Class Simple
    Public Shared Sub Main()
        ' The Simple class controls access to the token source.
        Dim cts As New CancellationTokenSource()

        Console.WriteLine("Press 'C' to terminate the application..." + vbCrLf)
        ' Allow the UI thread to capture the token source, so that it
        ' can issue the cancel command.
        Dim t1 As New Thread(Sub()
                                 If Console.ReadKey(true).KeyChar.ToString().ToUpperInvariant() = "C" Then
                                     cts.Cancel()
                                 End If
                             End Sub)

        ' ServerClass sees only the token, not the token source.
        Dim t2 As New Thread(New ParameterizedThreadStart(AddressOf ServerClass.StaticMethod))

        ' Start the UI thread.
        t1.Start()

        ' Start the worker thread and pass it the token.
        t2.Start(cts.Token)

        t2.Join()
        cts.Dispose()
    End Sub
End Class
' The example displays the following output:
'       Press 'C' to terminate the application...
'
'       ServerClass.StaticMethod is running on another thread.
'       The worker thread has been canceled. Press any key to exit.

Siehe auch

• Verwenden von Threads und Threading