CancellationTokenSource Sınıf

Tanım

public ref class CancellationTokenSource : IDisposable

public ref class CancellationTokenSource sealed : IDisposable

public class CancellationTokenSource : IDisposable

[System.Runtime.InteropServices.ComVisible(false)]
public sealed class CancellationTokenSource : IDisposable

[System.Runtime.InteropServices.ComVisible(false)]
public class CancellationTokenSource : IDisposable

type CancellationTokenSource = class
    interface IDisposable

[<System.Runtime.InteropServices.ComVisible(false)>]
type CancellationTokenSource = class
    interface IDisposable

Public Class CancellationTokenSource
Implements IDisposable

Public NotInheritable Class CancellationTokenSource
Implements IDisposable

Devralma

Object

CancellationTokenSource

Öznitelikler

ComVisibleAttribute

Uygulamalar

IDisposable

Örnekler

Aşağıdaki örnek, on iki farklı gereçden 10 integral değeri okuyan bir veri toplama uygulamasına öykünmek için rastgele bir sayı Oluşturucu kullanır.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. Sıfır değeri, ölçümün bir gereç için başarısız olduğunu gösterir, bu durumda işlem iptal edilmelidir ve genel bir ortalama hesaplanmamalıdır.A value of zero indicates that the measurement has failed for one instrument, in which case the operation should be cancelled and no overall mean should be computed.

İşlemin olası iptalinin işlenmesi için, örnek bir CancellationTokenSource nesneye iletilen bir iptal belirteci üreten bir nesne oluşturur TaskFactory .To handle the possible cancellation of the operation, the example instantiates a CancellationTokenSource object that generates a cancellation token which is passed to a TaskFactory object. TaskFactoryİçindeki nesnesi, belirli bir gereç için readusing 'leri toplamaktan sorumlu görevlerin her birine iptal belirtecini geçirir.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken)Yöntemi, ortalaması yalnızca tüm kullanımlar başarıyla toplandıktan sonra hesaplandığından emin olmak için çağrılır.The TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) method is called to ensure that the mean is computed only after all readings have been gathered successfully. Bir görev iptal edildiğinden, TaskFactory.ContinueWhenAll Yöntem çağrısı bir özel durum oluşturur.If a task has not because it has been cancelled, the call to the TaskFactory.ContinueWhenAll method throws an exception.

using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;

public class Example
{
   public static void Main()
   {
      // Define the cancellation token.
      CancellationTokenSource source = new CancellationTokenSource();
      CancellationToken token = source.Token;

      Random rnd = new Random();
      Object lockObj = new Object();
      
      List<Task<int[]>> tasks = new List<Task<int[]>>();
      TaskFactory factory = new TaskFactory(token);
      for (int taskCtr = 0; taskCtr <= 10; taskCtr++) {
         int iteration = taskCtr + 1;
         tasks.Add(factory.StartNew( () => {
                                       int value;
                                       int[] values = new int[10];
                                       for (int ctr = 1; ctr <= 10; ctr++) {
                                          lock (lockObj) {
                                             value = rnd.Next(0,101);
                                          }
                                          if (value == 0) { 
                                             source.Cancel();
                                             Console.WriteLine("Cancelling at task {0}", iteration);
                                             break;
                                          }   
                                          values[ctr-1] = value; 
                                       }
                                       return values;
                                    }, token));   
      }
      try {
         Task<double> fTask = factory.ContinueWhenAll(tasks.ToArray(), 
                                                      (results) => {
                                                         Console.WriteLine("Calculating overall mean...");
                                                         long sum = 0;
                                                         int n = 0; 
                                                         foreach (var t in results) {
                                                            foreach (var r in t.Result) {
                                                                  sum += r;
                                                                  n++;
                                                               }
                                                         }
                                                         return sum/(double) n;
                                                      } , token);
         Console.WriteLine("The mean is {0}.", fTask.Result);
      }   
      catch (AggregateException ae) {
         foreach (Exception e in ae.InnerExceptions) {
            if (e is TaskCanceledException)
               Console.WriteLine("Unable to compute mean: {0}", 
                                 ((TaskCanceledException) e).Message);
            else
               Console.WriteLine("Exception: " + e.GetType().Name);
         }
      }
      finally {
         source.Dispose();
      }
   }
}
// Repeated execution of the example produces output like the following:
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 10
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 5.29545454545455.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 6
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 4.97363636363636.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 5
//       Unable to compute mean: A task was canceled.
//       
//       Cancelling at task 4
//       Unable to compute mean: A task was canceled.
//       
//       Calculating overall mean...
//       The mean is 4.86545454545455.

Imports System.Collections.Generic
Imports System.Threading
Imports System.Threading.Tasks

Module Example
   Public Sub Main()
      ' Define the cancellation token.
      Dim source As New CancellationTokenSource()
      Dim token As CancellationToken = source.Token

      Dim lockObj As New Object()
      Dim rnd As New Random

      Dim tasks As New List(Of Task(Of Integer()))
      Dim factory As New TaskFactory(token)
      For taskCtr As Integer = 0 To 10
         Dim iteration As Integer = taskCtr + 1
         tasks.Add(factory.StartNew(Function()
                                       Dim value, values(9) As Integer
                                       For ctr As Integer = 1 To 10
                                          SyncLock lockObj
                                             value = rnd.Next(0,101)
                                          End SyncLock
                                          If value = 0 Then 
                                             source.Cancel
                                             Console.WriteLine("Cancelling at task {0}", iteration)
                                             Exit For
                                          End If   
                                          values(ctr-1) = value 
                                       Next
                                       Return values
                                    End Function, token))   
         
      Next
      Try
         Dim fTask As Task(Of Double) = factory.ContinueWhenAll(tasks.ToArray(), 
                                                         Function(results)
                                                            Console.WriteLine("Calculating overall mean...")
                                                            Dim sum As Long
                                                            Dim n As Integer 
                                                            For Each t In results
                                                               For Each r In t.Result
                                                                  sum += r
                                                                  n+= 1
                                                               Next
                                                            Next
                                                            Return sum/n
                                                         End Function, token)
         Console.WriteLine("The mean is {0}.", fTask.Result)
      Catch ae As AggregateException
         For Each e In ae.InnerExceptions
            If TypeOf e Is TaskCanceledException
               Console.WriteLine("Unable to compute mean: {0}", 
                                 CType(e, TaskCanceledException).Message)
            Else
               Console.WriteLine("Exception: " + e.GetType().Name)
            End If   
         Next
      Finally
         source.Dispose()
      End Try                                                          
   End Sub
End Module
' Repeated execution of the example produces output like the following:
'       Cancelling at task 5
'       Unable to compute mean: A task was canceled.
'       
'       Cancelling at task 10
'       Unable to compute mean: A task was canceled.
'       
'       Calculating overall mean...
'       The mean is 5.29545454545455.
'       
'       Cancelling at task 4
'       Unable to compute mean: A task was canceled.
'       
'       Cancelling at task 5
'       Unable to compute mean: A task was canceled.
'       
'       Cancelling at task 6
'       Unable to compute mean: A task was canceled.
'       
'       Calculating overall mean...
'       The mean is 4.97363636363636.
'       
'       Cancelling at task 4
'       Unable to compute mean: A task was canceled.
'       
'       Cancelling at task 5
'       Unable to compute mean: A task was canceled.
'       
'       Cancelling at task 4
'       Unable to compute mean: A task was canceled.
'       
'       Calculating overall mean...
'       The mean is 4.86545454545455.

Açıklamalar

.NET Framework 4 ' te başlayarak, .NET Framework iki nesne içeren zaman uyumsuz veya uzun süreli zaman uyumlu işlemler için birlikte çalışan bir birleştirilmiş model kullanır:Starting with the .NET Framework 4, the .NET Framework uses a unified model for cooperative cancellation of asynchronous or long-running synchronous operations that involves two objects:

• CancellationTokenSourceKendi özelliği aracılığıyla iptal belirteci sağlayan Token ve ya da metodunu çağırarak bir iptal iletisi gönderen nesne Cancel CancelAfter .A CancellationTokenSource object, which provides a cancellation token through its Token property and sends a cancellation message by calling its Cancel or CancelAfter method.

• CancellationTokenİptalin istenip istenmediğini gösteren bir nesne.A CancellationToken object, which indicates whether cancellation is requested.

Birlikte çalışırken iptal modelinin uygulanması için genel bir örüntü şunlardır:The general pattern for implementing the cooperative cancellation model is:

• CancellationTokenSourceAyrı ayrı iptal belirteçlerine yönelik iptali bildirimini yöneten ve gönderen bir nesne örneği oluşturur.Instantiate a CancellationTokenSource object, which manages and sends cancellation notification to the individual cancellation tokens.

• Özelliği tarafından döndürülen belirteci, CancellationTokenSource.Token iptal için dinleyen her bir göreve veya iş parçacığına geçirin.Pass the token returned by the CancellationTokenSource.Token property to each task or thread that listens for cancellation.

• CancellationToken.IsCancellationRequestedİptal belirtecini alan işlemlerden yöntemi çağırın.Call the CancellationToken.IsCancellationRequested method from operations that receive the cancellation token. Her görev veya iş parçacığının bir iptal isteğine yanıt vermesi için bir mekanizma sağlar.Provide a mechanism for each task or thread to respond to a cancellation request. Bir işlemi iptal etmeyi seçip tam olarak nasıl yapadığınıza bağlı olarak, uygulama mantığınıza göre değişir.Whether you choose to cancel an operation, and exactly how you do it, depends on your application logic.

• CancellationTokenSource.Cancelİptal bildirimi sağlamak için yöntemini çağırın.Call the CancellationTokenSource.Cancel method to provide notification of cancellation. Bu CancellationToken.IsCancellationRequested , iptal belirtecinin her kopyasında özelliğini olarak ayarlar true .This sets the CancellationToken.IsCancellationRequested property on every copy of the cancellation token to true.

• DisposeNesnesiyle işiniz bittiğinde yöntemi çağırın CancellationTokenSource .Call the Dispose method when you are finished with the CancellationTokenSource object.

Daha fazla bilgi için bkz. yönetilen Iş parçacıklarında iptal.For more information, see Cancellation in Managed Threads.

Oluşturucular

Özellikler

Yöntemler

Şunlara uygulanır

İş Parçacığı Güvenliği

Tüm ortak ve korumalı üyeleri CancellationTokenSource iş parçacığı açısından güvenlidir ve, Dispose() yalnızca nesnedeki tüm işlemler tamamlandığında kullanılması gereken, özel durumu ile birden fazla iş parçacığından aynı anda kullanılabilir CancellationTokenSource .All public and protected members of CancellationTokenSource are thread-safe and may be used concurrently from multiple threads, with the exception of Dispose(), which must only be used when all other operations on the CancellationTokenSource object have completed.