CancellationTokenSource Class

Definition

Señala un objeto CancellationToken que debe cancelarse.Signals to a CancellationToken that it should be canceled.

public ref class CancellationTokenSource : IDisposable
public ref class CancellationTokenSource sealed : IDisposable
public class CancellationTokenSource : IDisposable
[System.Runtime.InteropServices.ComVisible(false)]
public sealed class CancellationTokenSource : IDisposable
[System.Runtime.InteropServices.ComVisible(false)]
public class CancellationTokenSource : IDisposable
type CancellationTokenSource = class
    interface IDisposable
Public Class CancellationTokenSource
Implements IDisposable
Public NotInheritable Class CancellationTokenSource
Implements IDisposable
Inheritance
CancellationTokenSource
Attributes
Implements

Examples

En el ejemplo siguiente se utiliza un generador de números aleatorios para emular una aplicación de recopilación de datos que lee 10 valores enteros de once instrumentos diferentes.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. Un valor de cero indica que se ha producido un error en la medida para un instrumento, en cuyo caso se debe cancelar la operación y no se debe calcular la media global.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.

Para controlar la posible cancelación de la operación, en el ejemplo se crea una instancia de un objeto CancellationTokenSource que genera un token de cancelación que se pasa a un objeto 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. A su vez, el objeto TaskFactory pasa el token de cancelación a cada una de las tareas responsables de recopilar las lecturas de un instrumento determinado.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. Se llama al método TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) para asegurarse de que la media se calcula solo después de que todas las lecturas se hayan recopilado correctamente.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 una tarea no se ha cancelado porque se ha cancelado, la llamada al método TaskFactory.ContinueWhenAll produce una excepción.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.

Remarks

A partir de la .NET Framework 4.NET Framework 4, el .NET Framework usa un modelo unificado para la cancelación cooperativa de operaciones asincrónicas o sincrónicas de ejecución prolongada que implican dos objetos: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:

El patrón general para implementar el modelo de cancelación cooperativa es:The general pattern for implementing the cooperative cancellation model is:

Para más información, consulte el tema sobre la cancelación en subprocesos administrados.For more information, see Cancellation in Managed Threads.

Important

Este tipo implementa la interfaz IDisposable.This type implements the IDisposable interface. Cuando haya terminado de utilizar una instancia del tipo, debe desecharla directa o indirectamente.When you have finished using an instance of the type, you should dispose of it either directly or indirectly. Para eliminar el tipo directamente, llame a su método Dispose en un bloque try/catch.To dispose of the type directly, call its Dispose method in a try/catch block. Para deshacerse de él indirectamente, use una construcción de lenguaje como using (en C#) o Using (en Visual Basic).To dispose of it indirectly, use a language construct such as using (in C#) or Using (in Visual Basic). Para más información, vea la sección "Uso de objetos que implementan IDisposable" en el tema de la interfaz IDisposable.For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

Constructors

CancellationTokenSource()

Inicializa una nueva instancia de la clase CancellationTokenSource.Initializes a new instance of the CancellationTokenSource class.

CancellationTokenSource(Int32)

Inicializa una nueva instancia de la clase CancellationTokenSource que se cancela después del retraso especificado en milisegundos.Initializes a new instance of the CancellationTokenSource class that will be canceled after the specified delay in milliseconds.

CancellationTokenSource(TimeSpan)

Inicializa una nueva instancia de la clase CancellationTokenSource que se cancela después del intervalo de tiempo especificado.Initializes a new instance of the CancellationTokenSource class that will be canceled after the specified time span.

Properties

IsCancellationRequested

Obtiene si se solicitó la cancelación de este CancellationTokenSource.Gets whether cancellation has been requested for this CancellationTokenSource.

Token

Obtiene el objeto CancellationToken asociado a CancellationTokenSource.Gets the CancellationToken associated with this CancellationTokenSource.

Methods

Cancel()

Comunica una solicitud de cancelación.Communicates a request for cancellation.

Cancel(Boolean)

Comunica una solicitud de cancelación y especifica si se deben procesar las devoluciones de llamada restantes y las operaciones cancelables si se produce una excepción.Communicates a request for cancellation, and specifies whether remaining callbacks and cancelable operations should be processed if an exception occurs.

CancelAfter(Int32)

Programa una operación de cancelación en este CancellationTokenSource después del número especificado de milisegundos.Schedules a cancel operation on this CancellationTokenSource after the specified number of milliseconds.

CancelAfter(TimeSpan)

Programa una operación de cancelación en este CancellationTokenSource después del intervalo de tiempo especificado.Schedules a cancel operation on this CancellationTokenSource after the specified time span.

CreateLinkedTokenSource(CancellationToken)
CreateLinkedTokenSource(CancellationToken, CancellationToken)

Crea un CancellationTokenSource que tendrá el estado cancelado cuando alguno de los tokens de origen tenga el estado cancelado.Creates a CancellationTokenSource that will be in the canceled state when any of the source tokens are in the canceled state.

CreateLinkedTokenSource(CancellationToken[])

Crea un CancellationTokenSource que tendrá el estado cancelado cuando alguno de los tokens de origen del la matriz especificada tenga el estado cancelado.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()

Libera todos los recursos usados por la instancia actual de la clase CancellationTokenSource.Releases all resources used by the current instance of the CancellationTokenSource class.

Equals(Object)

Determina si el objeto especificado es igual al objeto actual.Determines whether the specified object is equal to the current object.

(Inherited from Object)
GetHashCode()

Sirve como la función hash predeterminada.Serves as the default hash function.

(Inherited from Object)
GetType()

Obtiene el Type de la instancia actual.Gets the Type of the current instance.

(Inherited from Object)
MemberwiseClone()

Crea una copia superficial del Object actual.Creates a shallow copy of the current Object.

(Inherited from Object)
ToString()

Devuelve una cadena que representa el objeto actual.Returns a string that represents the current object.

(Inherited from Object)

Applies to

Thread Safety

Todos los miembros públicos y protegidos de CancellationTokenSource son seguros para subprocesos y se pueden usar simultáneamente desde varios subprocesos, con la excepción de Dispose(), que solo se debe usar cuando se hayan completado todas las demás operaciones en el objeto CancellationTokenSource.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.

See also