CancellationToken CancellationToken CancellationToken CancellationToken Struct

Définition

Propage une notification indiquant que des opérations doivent être annulées.Propagates notification that operations should be canceled.

public value class CancellationToken
[System.Runtime.InteropServices.ComVisible(false)]
public struct CancellationToken
type CancellationToken = struct
Public Structure CancellationToken
Héritage
CancellationTokenCancellationTokenCancellationTokenCancellationToken
Attributs

Exemples

L’exemple suivant utilise un générateur de nombres aléatoires pour émuler une application de collecte de données qui lit 10 valeurs intégrales à partir de onze instruments différents.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. La valeur zéro indique que la mesure a échoué pour un instrument. dans ce cas, l’opération doit être annulée et aucune moyenne globale ne doit être calculée.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.

Pour gérer l’annulation possible de l’opération, l’exemple instancie un objet CancellationTokenSource qui génère un jeton d’annulation qui est passé à un objet 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. L’objet TaskFactory transmet à son tour le jeton d’annulation à chacune des tâches responsables de la collecte des lectures d’un instrument particulier.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. La méthode TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) est appelée pour garantir que la moyenne est calculée uniquement une fois que toutes les lectures ont été collectées avec succès.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. Si une tâche n’a pas été annulée, l’appel à la méthode TaskFactory.ContinueWhenAll lève une exception.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.

Remarques

Un CancellationToken permet l’annulation coopérative entre les threads, les éléments de travail du pool de threads ou les objets Task.A CancellationToken enables cooperative cancellation between threads, thread pool work items, or Task objects. Vous créez un jeton d’annulation en instanciant un objet CancellationTokenSource, qui gère les jetons d’annulation récupérés à partir de sa propriété CancellationTokenSource.Token.You create a cancellation token by instantiating a CancellationTokenSource object, which manages cancellation tokens retrieved from its CancellationTokenSource.Token property. Vous transmettez ensuite le jeton d’annulation à un nombre quelconque de threads, tâches ou opérations qui doivent recevoir une notification d’annulation.You then pass the cancellation token to any number of threads, tasks, or operations that should receive notice of cancellation. Le jeton ne peut pas être utilisé pour initier l’annulation.The token cannot be used to initiate cancellation. Lorsque l’objet propriétaire appelle CancellationTokenSource.Cancel, la propriété IsCancellationRequested sur chaque copie du jeton d’annulation a la valeur true.When the owning object calls CancellationTokenSource.Cancel, the IsCancellationRequested property on every copy of the cancellation token is set to true. Les objets qui reçoivent la notification peuvent répondre de la manière qui convient.The objects that receive the notification can respond in whatever manner is appropriate.

Pour plus d’informations et des exemples de code, consultez annulation dans les threads managés.For more information and code examples see Cancellation in Managed Threads.

Constructeurs

CancellationToken(Boolean) CancellationToken(Boolean) CancellationToken(Boolean) CancellationToken(Boolean)

Initialise la CancellationToken.Initializes the CancellationToken.

Propriétés

CanBeCanceled CanBeCanceled CanBeCanceled CanBeCanceled

Détermine si ce jeton peut être à l'état Annulé.Gets whether this token is capable of being in the canceled state.

IsCancellationRequested IsCancellationRequested IsCancellationRequested IsCancellationRequested

Détermine si l'annulation a été demandée pour ce jeton.Gets whether cancellation has been requested for this token.

None None None None

Retourne une valeur CancellationToken vide.Returns an empty CancellationToken value.

WaitHandle WaitHandle WaitHandle WaitHandle

Obtient un WaitHandle qui est signalé lors de l'annulation du jeton.Gets a WaitHandle that is signaled when the token is canceled.

Méthodes

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Détermine si l'instance actuelle de CancellationToken est égale au Object spécifié.Determines whether the current CancellationToken instance is equal to the specified Object.

Equals(CancellationToken) Equals(CancellationToken) Equals(CancellationToken) Equals(CancellationToken)

Détermine si l'instance actuelle de CancellationToken est égale au jeton spécifié.Determines whether the current CancellationToken instance is equal to the specified token.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Sert de fonction de hachage pour un CancellationToken.Serves as a hash function for a CancellationToken.

Register(Action) Register(Action) Register(Action) Register(Action)

Inscrit un délégué qui sera appelé lors de l'annulation du CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action, Boolean) Register(Action, Boolean) Register(Action, Boolean) Register(Action, Boolean)

Inscrit un délégué qui sera appelé lors de l'annulation du CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object) Register(Action<Object>, Object) Register(Action<Object>, Object) Register(Action<Object>, Object)

Inscrit un délégué qui sera appelé lors de l'annulation du CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean)

Inscrit un délégué qui sera appelé lors de l'annulation du CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

ThrowIfCancellationRequested() ThrowIfCancellationRequested() ThrowIfCancellationRequested() ThrowIfCancellationRequested()

Lève une OperationCanceledException si l'annulation de ce jeton a été demandée.Throws a OperationCanceledException if this token has had cancellation requested.

UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object)

Inscrit un délégué qui est appelé quand ce CancellationToken est annulé.Registers a delegate that is called when this CancellationToken is canceled.

Opérateurs

Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken)

Détermine si deux instances CancellationToken sont égales.Determines whether two CancellationToken instances are equal.

Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken)

Détermine si les deux instances de CancellationToken ne sont pas égales.Determines whether two CancellationToken instances are not equal.

S’applique à

Cohérence de thread

Tous les membres publics et protégés de CancellationToken sont thread-safe et peuvent être utilisés simultanément par plusieurs threads.All public and protected members of CancellationToken are thread-safe and may be used concurrently from multiple threads.

Voir aussi