CancellationToken.IsCancellationRequested Properti

Definisi

Ruang nama:

System.Threading

Rakitan:

netstandard.dll, System.Runtime.dll

Sumber:

CancellationToken.cs

Mendapatkan apakah pembatalan telah diminta untuk token ini.

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

public bool IsCancellationRequested { get; }

member this.IsCancellationRequested : bool

Public ReadOnly Property IsCancellationRequested As Boolean

Nilai Properti

Boolean

true jika pembatalan telah diminta untuk token ini; jika tidak, false.

Contoh

Berikut ini adalah contoh sederhana yang menjalankan proses server hingga IsCancellationRequested properti mengembalikan true.

using System;
using System.Threading;

public class ServerClass
{
   public static void StaticMethod(object obj)
   {
      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.

Contoh membuat instans CancellationTokenSource objek, yang mengontrol akses ke token pembatalan. Kemudian mendefinisikan dua prosedur utas. Yang pertama didefinisikan sebagai ekspresi lambda yang mengumpulkan keyboard dan, ketika tombol "C" ditekan, memanggil CancellationTokenSource.Cancel untuk mengatur token pembatalan ke status dibatalkan. Yang kedua adalah metode berparameter, ServerClass.StaticMethod, yang menjalankan perulangan hingga IsCancellationRequested properti adalah true.

Utas utama kemudian memulai dua utas dan blok hingga utas ServerClass.StaticMethod yang menjalankan metode berakhir.

Keterangan

Properti ini menunjukkan apakah pembatalan telah diminta untuk token ini, baik melalui token awalnya sedang dibangun dalam status dibatalkan, atau melalui panggilan Cancel pada token yang terkait CancellationTokenSource.

Jika properti ini adalah true, itu hanya menjamin bahwa pembatalan telah diminta. Ini tidak menjamin bahwa setiap handler terdaftar telah selesai dieksekusi, atau permintaan pembatalan telah selesai disebarkan ke semua handler terdaftar. Sinkronisasi tambahan mungkin diperlukan, terutama dalam situasi di mana objek terkait dibatalkan secara bersamaan.

Lihat juga

• Pembatalan
• Pembatalan Tugas