CancellationTokenSource CancellationTokenSource CancellationTokenSource CancellationTokenSource Class

Definizione

Segnala a un oggetto CancellationToken che deve essere annullato.Signals to a CancellationToken that it should be canceled.

public ref class CancellationTokenSource : IDisposable
[System.Runtime.InteropServices.ComVisible(false)]
public class CancellationTokenSource : IDisposable
type CancellationTokenSource = class
    interface IDisposable
Public Class CancellationTokenSource
Implements IDisposable
Ereditarietà
CancellationTokenSourceCancellationTokenSourceCancellationTokenSourceCancellationTokenSource
Attributi
Implementazioni

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

A partire dal .NET Framework 4.NET Framework 4, .NET Framework Usa un modello unificato per l'annullamento cooperativo di operazioni sincrone asincrone o con esecuzione prolungata che sono necessari due oggetti:Starting with the .NET Framework 4.NET Framework 4, the .NET Framework uses a unified model for cooperative cancellation of asynchronous or long-running synchronous operations that involves two objects:

Il criterio generale per implementare il modello di annullamento cooperativo è il seguente:The general pattern for implementing the cooperative cancellation model is:

Per altre informazioni, vedere Annullamento in thread gestiti.For more information, see Cancellation in Managed Threads.

Importante

Questo tipo implementa la IDisposable interfaccia.This type implements the IDisposable interface. Dopo aver utilizzando un'istanza del tipo, è necessario eliminarlo direttamente o indirettamente.When you have finished using an instance of the type, you should dispose of it either directly or indirectly. Per eliminare il tipo direttamente, chiamare relativi Dispose metodo in un try / catch blocco.To dispose of the type directly, call its Dispose method in a try/catch block. Per eliminarlo indirettamente, utilizzare un costrutto di linguaggio come ad esempio using in C# o Using in Visual Basic.To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). Per altre informazioni, vedere la sezione "Utilizzo di oggetti che implementano IDisposable" nel IDisposable argomento relativo all'interfaccia.For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

Costruttori

CancellationTokenSource() CancellationTokenSource() CancellationTokenSource() CancellationTokenSource()

Inizializza una nuova istanza della classe CancellationTokenSource.Initializes a new instance of the CancellationTokenSource class.

CancellationTokenSource(Int32) CancellationTokenSource(Int32) CancellationTokenSource(Int32) CancellationTokenSource(Int32)

Inizializza una nuova istanza della classe CancellationTokenSource che verrà annullata dopo il ritardo specificato in millisecondi.Initializes a new instance of the CancellationTokenSource class that will be canceled after the specified delay in milliseconds.

CancellationTokenSource(TimeSpan) CancellationTokenSource(TimeSpan) CancellationTokenSource(TimeSpan) CancellationTokenSource(TimeSpan)

Inizializza una nuova istanza della classe CancellationTokenSource che verrà annullata dopo l'intervallo di tempo specificato.Initializes a new instance of the CancellationTokenSource class that will be canceled after the specified time span.

Proprietà

IsCancellationRequested IsCancellationRequested IsCancellationRequested IsCancellationRequested

Ottiene un valore che indica se per CancellationTokenSource è stato richiesto l'annullamento.Gets whether cancellation has been requested for this CancellationTokenSource.

Token Token Token Token

Ottiene l'oggetto CancellationToken associato a questo oggetto CancellationTokenSource.Gets the CancellationToken associated with this CancellationTokenSource.

Metodi

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.

CancelAfter(Int32) CancelAfter(Int32) CancelAfter(Int32) CancelAfter(Int32)

Programma un'operazione di annullamento in questo oggetto CancellationTokenSource dopo il numero di millisecondi specificato.Schedules a cancel operation on this CancellationTokenSource after the specified number of milliseconds.

CancelAfter(TimeSpan) CancelAfter(TimeSpan) CancelAfter(TimeSpan) CancelAfter(TimeSpan)

Programma un'operazione di annullamento in questo oggetto CancellationTokenSource dopo l'intervallo di tempo specificato.Schedules a cancel operation on this CancellationTokenSource after the specified time span.

CreateLinkedTokenSource(CancellationToken, CancellationToken) CreateLinkedTokenSource(CancellationToken, CancellationToken) CreateLinkedTokenSource(CancellationToken, CancellationToken) CreateLinkedTokenSource(CancellationToken, CancellationToken)

Crea un oggetto CancellationTokenSource che sarà in stato annullato quando uno dei token di origine si troverà in stato annullato.Creates a CancellationTokenSource that will be in the canceled state when any of the source tokens are in the canceled state.

CreateLinkedTokenSource(CancellationToken[]) CreateLinkedTokenSource(CancellationToken[]) CreateLinkedTokenSource(CancellationToken[]) CreateLinkedTokenSource(CancellationToken[])

Crea un oggetto CancellationTokenSource che sarà nello stato annullato quando uno dei token di origine nella matrice specificata si troverà nello stato annullato.Creates a CancellationTokenSource that will be in the canceled state when any of the source tokens in the specified array are in the canceled state.

Dispose() Dispose() Dispose() Dispose()

Rilascia tutte le risorse usate dall'istanza corrente della classe CancellationTokenSource.Releases all resources used by the current instance of the CancellationTokenSource class.

Dispose(Boolean) Dispose(Boolean) Dispose(Boolean) Dispose(Boolean)

Rilascia le risorse non gestite usate dalla classe CancellationTokenSource e facoltativamente le risorse gestite.Releases the unmanaged resources used by the CancellationTokenSource class and optionally releases the managed resources.

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

Determina se l'oggetto specificato è uguale all'oggetto corrente.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Funge da funzione hash predefinita.Serves as the default hash function.

(Inherited from Object)
GetType() GetType() GetType() GetType()

Ottiene l'oggetto Type dell'istanza corrente.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone() MemberwiseClone() MemberwiseClone() MemberwiseClone()

Crea una copia superficiale dell'oggetto Object corrente.Creates a shallow copy of the current Object.

(Inherited from Object)
ToString() ToString() ToString() ToString()

Restituisce una stringa che rappresenta l'oggetto corrente.Returns a string that represents the current object.

(Inherited from Object)

Si applica a

Thread safety

Tutti i membri pubblici e protetti della CancellationTokenSource sono thread-safe e possono essere utilizzati contemporaneamente da più thread, ad eccezione di Dispose(), che deve essere usata solo quando tutte le altre operazioni su di CancellationTokenSource oggetto completati.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.

Vedi anche