CancellationTokenSource.Cancel Metoda

Definicja

Komunikuje żądanie anulowania.Communicates a request for cancellation.

Przeciążenia

Cancel()

Komunikuje żądanie anulowania.Communicates a request for cancellation.

Cancel(Boolean)

Komunikuje żądanie anulowania i określa, czy pozostałe wywołania zwrotne i operacje anulowania powinny być przetwarzane, jeśli wystąpi wyjątek.Communicates a request for cancellation, and specifies whether remaining callbacks and cancelable operations should be processed if an exception occurs.

Cancel()

Komunikuje żądanie anulowania.Communicates a request for cancellation.

public:
 void Cancel();
public void Cancel ();
member this.Cancel : unit -> unit
Public Sub Cancel ()

Wyjątki

Ten CancellationTokenSource został usunięty.This CancellationTokenSource has been disposed.

Wyjątek agregujący zawierający wszystkie wyjątki zgłoszone przez zarejestrowane wywołania zwrotne w skojarzonym CancellationToken.An aggregate exception containing all the exceptions thrown by the registered callbacks on the associated CancellationToken.

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

Skojarzona CancellationToken zostanie powiadomiona o anulowaniu i przejdzie do stanu, w którym IsCancellationRequested zwraca wartość true.The associated CancellationToken will be notified of the cancellation and will transition to a state where IsCancellationRequested returns true.

Wszystkie wywołania zwrotne lub operacje anulowania zarejestrowane w CancellationToken zostaną wykonane.Any callbacks or cancelable operations registered with the CancellationToken will be executed.

Zalecamy, aby operacje anulowania i wywołania zwrotne zarejestrowane z CancellationToken nie generować wyjątków.We recommend that cancelable operations and callbacks registered with CancellationToken not throw exceptions.

To Przeciążenie anulowania spowoduje zagregowanie wszelkich wyjątków zgłoszonych do AggregateException, takich jak jedno wywołanie zwrotne zgłaszające wyjątek nie uniemożliwi wykonywania innych zarejestrowanych wywołań zwrotnych.This overload of Cancel will aggregate any exceptions thrown into an AggregateException, such that one callback throwing an exception will not prevent other registered callbacks from being executed.

Zobacz też

Cancel(Boolean)

Komunikuje żądanie anulowania i określa, czy pozostałe wywołania zwrotne i operacje anulowania powinny być przetwarzane, jeśli wystąpi wyjątek.Communicates a request for cancellation, and specifies whether remaining callbacks and cancelable operations should be processed if an exception occurs.

public:
 void Cancel(bool throwOnFirstException);
public void Cancel (bool throwOnFirstException);
member this.Cancel : bool -> unit
Public Sub Cancel (throwOnFirstException As Boolean)

Parametry

throwOnFirstException
Boolean

true, czy wyjątki powinny być natychmiast propagowane; w przeciwnym razie false.true if exceptions should immediately propagate; otherwise, false.

Wyjątki

Ten CancellationTokenSource został usunięty.This CancellationTokenSource has been disposed.

Wyjątek agregujący zawierający wszystkie wyjątki zgłoszone przez zarejestrowane wywołania zwrotne w skojarzonym CancellationToken.An aggregate exception containing all the exceptions thrown by the registered callbacks on the associated CancellationToken.

Uwagi

Skojarzona CancellationToken zostanie powiadomiona o anulowaniu i przejdzie do stanu, w którym IsCancellationRequested zwróci true.The associated CancellationToken will be notified of the cancellation and will transition to a state where IsCancellationRequested returns true.

Wszystkie wywołania zwrotne lub operacje anulowania zarejestrowane w CancellationToken zostaną wykonane.Any callbacks or cancelable operations registered with the CancellationToken will be executed. Wywołania zwrotne będą wykonywane synchronicznie w kolejności kolejki LIFO.Callbacks will be executed synchronously in LIFO order.

Zalecamy, aby operacje anulowania i wywołania zwrotne zarejestrowane z CancellationToken nie generować wyjątków.We recommend that cancelable operations and callbacks registered with CancellationToken not throw exceptions.

Jeśli throwOnFirstException jest true, wyjątek zostanie natychmiast rozpropagowany z wywołania do Cancel, co uniemożliwia przetworzenie pozostałych operacji wywołania zwrotnego i anulowanie.If throwOnFirstException is true, an exception will immediately propagate out of the call to Cancel, preventing the remaining callbacks and cancelable operations from being processed.

Jeśli throwOnFirstException jest false, to Przeciążenie spowoduje agregowanie wszelkich wyjątków zgłoszonych do AggregateException, takich jak jedno wywołanie zwrotne zgłaszające wyjątek nie uniemożliwi wykonywania innych zarejestrowanych wywołań zwrotnych.If throwOnFirstException is false, this overload will aggregate any exceptions thrown into an AggregateException, such that one callback throwing an exception will not prevent other registered callbacks from being executed.

Zobacz też

Dotyczy