CancellationToken CancellationToken CancellationToken CancellationToken Struct

Определение

Распространяет уведомление о том, что операции следует отменить.Propagates notification that operations should be canceled.

public value class CancellationToken
[System.Runtime.InteropServices.ComVisible(false)]
public struct CancellationToken
type CancellationToken = struct
Public Structure CancellationToken
Наследование
CancellationTokenCancellationTokenCancellationTokenCancellationToken
Атрибуты

Примеры

В следующем примере генератор случайных чисел используется для эмуляции приложения сбора данных, которое считывает 10 целочисленных значений из одиннадцати различных инструментов.The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. Нулевое значение указывает на то, что измерение завершилось ошибкой для одного инструмента. в этом случае операция должна быть отменена, а общее среднее значение не должно вычисляться.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.

Чтобы справиться с возможной отменой операции, в примере создается объект CancellationTokenSource, создающий токен отмены, который передается в объект 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. Объект TaskFactory, в свою очередь, передает маркер отмены каждой из задач, ответственных за сбор данных для конкретного инструмента.The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. Метод TaskFactory.ContinueWhenAll<TAntecedentResult,TResult>(Task<TAntecedentResult>[], Func<Task<TAntecedentResult>[],TResult>, CancellationToken) вызывается для того, чтобы среднее значение вычисляется только после успешного сбора всех считываний.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. Если задача не выполнена, поскольку она была отменена, вызов метода TaskFactory.ContinueWhenAll вызывает исключение.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.

Комментарии

@No__t-0 позволяет совместно выполнять отмену между потоками, рабочими элементами пула потоков или объектами Task.A CancellationToken enables cooperative cancellation between threads, thread pool work items, or Task objects. Токен отмены создается путем создания экземпляра объекта CancellationTokenSource, который управляет токенами отмены, полученными из свойства CancellationTokenSource.Token.You create a cancellation token by instantiating a CancellationTokenSource object, which manages cancellation tokens retrieved from its CancellationTokenSource.Token property. Затем токен отмены передается в любое количество потоков, задач или операций, которые должны получить уведомление об отмене.You then pass the cancellation token to any number of threads, tasks, or operations that should receive notice of cancellation. Токен нельзя использовать для инициации отмены.The token cannot be used to initiate cancellation. Когда владеющий объект вызывает CancellationTokenSource.Cancel, свойству IsCancellationRequested каждой копии токена отмены присваивается значение true.When the owning object calls CancellationTokenSource.Cancel, the IsCancellationRequested property on every copy of the cancellation token is set to true. Объекты, получающие уведомление, могут отвечать любым необходимым способом.The objects that receive the notification can respond in whatever manner is appropriate.

Дополнительные сведения и примеры кода см. в разделе об отмене в управляемых потоках.For more information and code examples see Cancellation in Managed Threads.

Конструкторы

CancellationToken(Boolean) CancellationToken(Boolean) CancellationToken(Boolean) CancellationToken(Boolean)

Инициализирует объект CancellationToken.Initializes the CancellationToken.

Свойства

CanBeCanceled CanBeCanceled CanBeCanceled CanBeCanceled

Возвращает значение, указывающее, может ли данный токен находиться в отмененном состоянии.Gets whether this token is capable of being in the canceled state.

IsCancellationRequested IsCancellationRequested IsCancellationRequested IsCancellationRequested

Возвращает значение, указывающее, есть ли для данного токена запрос на отмену.Gets whether cancellation has been requested for this token.

None None None None

Возвращает пустое значение CancellationToken.Returns an empty CancellationToken value.

WaitHandle WaitHandle WaitHandle WaitHandle

Возвращает дескриптор WaitHandle, получающий сигнал при отмене токена.Gets a WaitHandle that is signaled when the token is canceled.

Методы

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

Определяет, равен ли текущий экземпляр CancellationToken заданному объекту Object.Determines whether the current CancellationToken instance is equal to the specified Object.

Equals(CancellationToken) Equals(CancellationToken) Equals(CancellationToken) Equals(CancellationToken)

Определяет, равен ли текущий экземпляр CancellationToken заданному токену.Determines whether the current CancellationToken instance is equal to the specified token.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Служит хэш-функцией для CancellationToken.Serves as a hash function for a CancellationToken.

Register(Action) Register(Action) Register(Action) Register(Action)

Регистрирует делегат, который будет вызываться при отмене данного токена CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action, Boolean) Register(Action, Boolean) Register(Action, Boolean) Register(Action, Boolean)

Регистрирует делегат, который будет вызываться при отмене данного токена CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object) Register(Action<Object>, Object) Register(Action<Object>, Object) Register(Action<Object>, Object)

Регистрирует делегат, который будет вызываться при отмене данного токена CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean) Register(Action<Object>, Object, Boolean)

Регистрирует делегат, который будет вызываться при отмене данного токена CancellationToken.Registers a delegate that will be called when this CancellationToken is canceled.

ThrowIfCancellationRequested() ThrowIfCancellationRequested() ThrowIfCancellationRequested() ThrowIfCancellationRequested()

Создает исключение OperationCanceledException, если для данного токена есть запрос на отмену.Throws a OperationCanceledException if this token has had cancellation requested.

UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object) UnsafeRegister(Action<Object>, Object)

Регистрирует делегат, который вызывается при отмене данного токена CancellationToken.Registers a delegate that is called when this CancellationToken is canceled.

Операторы

Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken) Equality(CancellationToken, CancellationToken)

Определяет, равны ли два экземпляра CancellationToken.Determines whether two CancellationToken instances are equal.

Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken) Inequality(CancellationToken, CancellationToken)

Определяет, действительно ли два экземпляра CancellationToken не равны.Determines whether two CancellationToken instances are not equal.

Применяется к

Потокобезопасность

Все открытые и защищенные члены CancellationToken являются потокобезопасными и могут использоваться одновременно из нескольких потоков.All public and protected members of CancellationToken are thread-safe and may be used concurrently from multiple threads.

Дополнительно