CancellationTokenSource Clase

Definición

Señala un objeto CancellationToken que debe cancelarse.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
Herencia
CancellationTokenSource
Atributos
Implementaciones

Ejemplos

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 CancellationTokenSource una instancia de un objeto que genera un token de cancelación TaskFactory que se pasa a un objeto.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 TaskFactory su vez, el objeto 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 para asegurarse de que la media se calcula solo después de que todas las lecturas se hayan recopilado correctamente. TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken)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 TaskFactory.ContinueWhenAll llamada al método 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.

Comentarios

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

Importante

Este tipo implementa la IDisposable interfaz.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 Dispose método en un try / catch bloque.To dispose of the type directly, call its Dispose method in a try/catch block. Para deshacerse indirectamente, use una construcción using de lenguaje como (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 obtener más información, vea la sección "usar un objeto que implementa IDisposable" en el IDisposable tema sobre la interfaz.For more information, see the "Using an Object that Implements IDisposable" section in the IDisposable interface topic.

Constructores

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 de 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 de CancellationTokenSource que se cancela después de la duración especificada.Initializes a new instance of the CancellationTokenSource class that will be canceled after the specified time span.

Propiedades

IsCancellationRequested

Obtiene si se ha solicitado la cancelación de este objeto 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.

Métodos

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 de la duración especificada.Schedules a cancel operation on this CancellationTokenSource after the specified time span.

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 objeto 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.

Dispose(Boolean)

Libera los recursos no administrados utilizados por la clase CancellationTokenSource y, de forma opcional, libera los recursos administrados.Releases the unmanaged resources used by the CancellationTokenSource class and optionally releases the managed resources.

Equals(Object)

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

(Heredado de Object)
GetHashCode()

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

(Heredado de Object)
GetType()

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

(Heredado de Object)
MemberwiseClone()

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

(Heredado de Object)
ToString()

Devuelve un valor de tipo string que representa el objeto actual.Returns a string that represents the current object.

(Heredado de Object)

Se aplica a

Seguridad para subprocesos

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

Consulte también: