Propagates notification that operations should be canceled.
Assemblies: System.Threading.Tasks (in System.Threading.Tasks.dll)
mscorlib (in mscorlib.dll)
Thetype exposes the following members.
|Equals(CancellationToken)||Determines whether the current instance is equal to the specified token.|
|Equals(Object)||Determines whether the current instance is equal to the specified Object. (Overrides ValueType.Equals(Object).)|
|GetHashCode||Serves as a hash function for a . (Overrides ValueType.GetHashCode().)|
|GetType||Gets the Type of the current instance. (Inherited from Object.)|
|Register(Action)||Registers a delegate that will be called when this is canceled.|
|Register(Action, Boolean)||Registers a delegate that will be called when this is canceled.|
|Register(Action(Object), Object)||Registers a delegate that will be called when this is canceled.|
|Register(Action(Object), Object, Boolean)||Registers a delegate that will be called when this is canceled.|
|ThrowIfCancellationRequested||Throws a OperationCanceledException if this token has had cancellation requested.|
|ToString||Returns the fully qualified type name of this instance. (Inherited from ValueType.)|
A enables cooperative cancellation between threads, thread pool work items, or Task objects. You create a cancellation token by instantiating a CancellationTokenSource object, which manages cancellation tokens retrieved from its CancellationTokenSource.Token property. You then pass the cancellation token to any number of threads, tasks, or operations that should receive notice of cancellation. The token cannot be used to initiate cancellation. When the owning object calls CancellationTokenSource.Cancel, the IsCancellationRequested property on every copy of the cancellation token is set to true. The objects that receive the notification can respond in whatever manner is appropriate.
For more information and code examples see Cancellation in Managed Threads.
The following example uses a random number generator to emulate a data collection application that reads 10 integral values from eleven different instruments. 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.
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. The TaskFactory object in turn passes the cancellation token to each of the tasks responsible for collecting readings for a particular instrument. 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. If a task has not because it has been cancelled, the call to the TaskFactory.ContinueWhenAll method throws an exception.