スレッドの協調的な取り消し

.NET Framework 4 より前のバージョンでは、開始後にスレッドを協調的に取り消す組み込み方法が .NET に用意されていませんでした。 ただし、.NET Framework 4 以降では、 System.Threading.CancellationToken を使用してスレッドを取り消すことができます。これは、 System.Threading.Tasks.Task オブジェクトまたは PLINQ クエリを取り消すために使用できるのと同様です。 System.Threading.Thread クラスはキャンセル トークンの組み込みサポートを提供していませんが、Thread デリゲートを受け取るParameterizedThreadStart コンストラクターを使用して、トークンをスレッド プロシージャに渡すことができます。 この方法を次の例に示します。

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.

こちらも参照ください

• スレッドとスレッド処理