CancellationTokenSource.Cancel CancellationTokenSource.Cancel CancellationTokenSource.Cancel CancellationTokenSource.Cancel Method

Definizione

Comunica una richiesta di annullamento.Communicates a request for cancellation.

Overload

Cancel() Cancel() Cancel() Cancel()

Comunica una richiesta di annullamento.Communicates a request for cancellation.

Cancel(Boolean) Cancel(Boolean) Cancel(Boolean) Cancel(Boolean)

Passa una richiesta di annullamento e specifica se i callback restanti e le operazioni annullabili devono essere elaborati se si verifica un'eccezione.Communicates a request for cancellation, and specifies whether remaining callbacks and cancelable operations should be processed if an exception occurs.

Cancel() Cancel() Cancel() Cancel()

Comunica una richiesta di annullamento.Communicates a request for cancellation.

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

Eccezioni

Eccezione di aggregazione che contiene tutte le eccezioni generate dai callback registrati sull'oggetto CancellationToken associato.An aggregate exception containing all the exceptions thrown by the registered callbacks on the associated CancellationToken.

Esempi

L'esempio seguente usa un generatore di numeri casuali per emulare un'applicazione di raccolta dati che legge i valori integrali 10 da undici vari strumenti.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. Un valore pari a zero indica che la misura non è riuscita per uno strumento, nel qual caso l'operazione deve essere annullata e non indicano complessivo deve essere calcolate.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.

Per gestire l'annullamento possibili dell'operazione, l'esempio crea un'istanza di un CancellationTokenSource oggetto che genera un token di annullamento che viene passato a un TaskFactory oggetto.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. Il TaskFactory oggetto a sua volta inoltra il token di annullamento per ognuna delle attività di responsabile per la raccolta di letture per uno strumento specifico.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. Il TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) metodo viene chiamato per verificare che la media viene calcolata solo dopo che tutte le letture sono state raccolte correttamente.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. Se è un'attività non perché è stata annullata, la chiamata al TaskFactory.ContinueWhenAll metodo genera un'eccezione.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.

Commenti

L'oggetto associato CancellationToken riceverà una notifica dell'annullamento e passerà a uno stato in cui IsCancellationRequested restituisce true.The associated CancellationToken will be notified of the cancellation and will transition to a state where IsCancellationRequested returns true.

Eventuali operazioni annullabili o un callback registrato con il CancellationToken verrà eseguito.Any callbacks or cancelable operations registered with the CancellationToken will be executed.

È consigliabile che operazioni annullabili e i callback registrato con CancellationToken non generano eccezioni.We recommend that cancelable operations and callbacks registered with CancellationToken not throw exceptions.

Questo overload di annullamento aggregherà le eccezioni generate in un AggregateException, in modo che un callback che genera un'eccezione non impedirà l'esecuzione di altri callback registrato.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.

Vedi anche

Cancel(Boolean) Cancel(Boolean) Cancel(Boolean) Cancel(Boolean)

Passa una richiesta di annullamento e specifica se i callback restanti e le operazioni annullabili devono essere elaborati se si verifica un'eccezione.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)

Parametri

throwOnFirstException
Boolean Boolean Boolean Boolean

true se le eccezioni devono essere propagate immediatamente; in caso contrario, false.true if exceptions should immediately propagate; otherwise, false.

Eccezioni

Eccezione di aggregazione che contiene tutte le eccezioni generate dai callback registrati sull'oggetto CancellationToken associato.An aggregate exception containing all the exceptions thrown by the registered callbacks on the associated CancellationToken.

Commenti

L'oggetto associato CancellationToken riceverà una notifica dell'annullamento e passerà a uno stato in cui IsCancellationRequested restituisce true.The associated CancellationToken will be notified of the cancellation and will transition to a state where IsCancellationRequested returns true.

Eventuali operazioni annullabili o un callback registrato con il CancellationToken verrà eseguito.Any callbacks or cancelable operations registered with the CancellationToken will be executed. Callback verranno eseguiti in modo sincrono in ordine LIFO.Callbacks will be executed synchronously in LIFO order.

È consigliabile che operazioni annullabili e i callback registrato con CancellationToken non generano eccezioni.We recommend that cancelable operations and callbacks registered with CancellationToken not throw exceptions.

Se throwOnFirstException viene true, un'eccezione verrà immediatamente propagata dalla chiamata a Cancel, impedendo il callback restanti e le operazioni annullabili dall'elaborazione.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.

Se throwOnFirstException viene false, questo overload aggregherà le eccezioni generate in un AggregateException, in modo che un callback che genera un'eccezione non impedirà l'esecuzione di altri callback registrato.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.

Vedi anche

Si applica a