CancellationToken Struktura

Definicja

Propaguje powiadomienie, że operacje powinny być anulowane.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
Dziedziczenie
CancellationToken
Atrybuty

Przykłady

Poniższy przykład używa generatora liczb losowych do emulowania aplikacji do zbierania danych, która odczytuje 10 wartości całkowitych z jedenastu różnych instrumentów.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. Wartość zero wskazuje, że pomiar nie powiódł się dla jednego instrumentu, w tym przypadku operacja powinna zostać anulowana i nie ma potrzeby obliczenia całkowitego średniego.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.

Aby obsłużyć możliwe anulowanie operacji, przykład tworzy obiekt CancellationTokenSource, który generuje token anulowania, który jest przesyłany do obiektu 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. Obiekt TaskFactory z kolei przekazuje token anulowania do każdego zadania odpowiedzialnego za zbieranie odczytów dla określonego instrumentu.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. Metoda TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) jest wywoływana, aby upewnić się, że średni jest obliczany dopiero po pomyślnym zebraniu wszystkich odczytów.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. Jeśli zadanie nie zostało, ponieważ zostało anulowane, wywołanie metody TaskFactory.ContinueWhenAll zgłasza wyjątek.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.

Uwagi

@No__t_0 umożliwia wspólne anulowanie między wątkami, elementami roboczymi puli wątków lub obiektami Task.A CancellationToken enables cooperative cancellation between threads, thread pool work items, or Task objects. Można utworzyć token anulowania przez utworzenie wystąpienia obiektu CancellationTokenSource, który zarządza tokenami anulowania pobranymi ze swojej właściwości CancellationTokenSource.Token.You create a cancellation token by instantiating a CancellationTokenSource object, which manages cancellation tokens retrieved from its CancellationTokenSource.Token property. Następnie można przekazać token anulowania do dowolnej liczby wątków, zadań lub operacji, które powinny otrzymywać powiadomienia o anulowaniu.You then pass the cancellation token to any number of threads, tasks, or operations that should receive notice of cancellation. Nie można użyć tokenu do inicjowania anulowania.The token cannot be used to initiate cancellation. Gdy obiekt będący właścicielem wywołuje CancellationTokenSource.Cancel, właściwość IsCancellationRequested dla każdej kopii tokenu anulowania ma ustawioną wartość true.When the owning object calls CancellationTokenSource.Cancel, the IsCancellationRequested property on every copy of the cancellation token is set to true. Obiekty otrzymujące powiadomienie mogą reagować w dowolny sposób.The objects that receive the notification can respond in whatever manner is appropriate.

Aby uzyskać więcej informacji i przykładów kodu, zobacz Anulowanie w zarządzanych wątkach.For more information and code examples see Cancellation in Managed Threads.

Konstruktory

CancellationToken(Boolean)

Inicjuje CancellationToken.Initializes the CancellationToken.

Właściwości

CanBeCanceled

Określa, czy ten token może być w stanie anulowany.Gets whether this token is capable of being in the canceled state.

IsCancellationRequested

Pobiera, czy dla tego tokenu zażądano anulowania.Gets whether cancellation has been requested for this token.

None

Zwraca pustą wartość CancellationToken.Returns an empty CancellationToken value.

WaitHandle

Pobiera WaitHandle, które są sygnalizowane, gdy token zostanie anulowany.Gets a WaitHandle that is signaled when the token is canceled.

Metody

Equals(CancellationToken)

Określa, czy bieżące wystąpienie CancellationToken jest równe określonemu tokenowi.Determines whether the current CancellationToken instance is equal to the specified token.

Equals(Object)

Określa, czy bieżące wystąpienie CancellationToken jest równe podanemu Object.Determines whether the current CancellationToken instance is equal to the specified Object.

GetHashCode()

Służy jako funkcja skrótu dla CancellationToken.Serves as a hash function for a CancellationToken.

Register(Action)

Rejestruje delegata, który zostanie wywołany, gdy CancellationToken zostanie anulowana.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action, Boolean)

Rejestruje delegata, który zostanie wywołany, gdy CancellationToken zostanie anulowana.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object)

Rejestruje delegata, który zostanie wywołany, gdy CancellationToken zostanie anulowana.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object, Boolean)

Rejestruje delegata, który zostanie wywołany, gdy CancellationToken zostanie anulowana.Registers a delegate that will be called when this CancellationToken is canceled.

ThrowIfCancellationRequested()

Zgłasza OperationCanceledException, jeśli ten token ma żądanie anulowania.Throws a OperationCanceledException if this token has had cancellation requested.

UnsafeRegister(Action<Object>, Object)

Rejestruje delegata, który jest wywoływany po anulowaniu tego CancellationToken.Registers a delegate that is called when this CancellationToken is canceled.

Operatory

Equality(CancellationToken, CancellationToken)

Określa, czy dwa wystąpienia CancellationToken są równe.Determines whether two CancellationToken instances are equal.

Inequality(CancellationToken, CancellationToken)

Określa, czy dwa wystąpienia CancellationToken nie są równe.Determines whether two CancellationToken instances are not equal.

Dotyczy

Bezpieczeństwo wątkowe

Wszystkie publiczne i chronione elementy członkowskie CancellationToken są bezpieczne dla wątków i mogą być używane współbieżnie z wielu wątków.All public and protected members of CancellationToken are thread-safe and may be used concurrently from multiple threads.

Zobacz też