/// <summary>
/// Returns a <see cref="Task"/> that is canceled when this <see cref="CancellationToken"/> is canceled. This method will leak resources if the cancellation token is long-lived; use <see cref="ToCancellationTokenTaskSource"/> for a similar approach with proper resource management.
/// </summary>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor.</param>
/// <returns>A <see cref="Task"/> that is canceled when this <see cref="CancellationToken"/> is canceled.</returns>
public static Task AsTask(this CancellationToken cancellationToken)
{
if (!cancellationToken.CanBeCanceled) {
return TaskConstants.Never;
}
if (cancellationToken.IsCancellationRequested) {
return TaskConstants.Canceled;
}
var tcs = new TaskCompletionSource();
cancellationToken.Register(() => tcs.TrySetCanceled(), false);
return tcs.Task;
}
/// <summary>
/// Creates a task for the specified cancellation token, registering with the token if necessary.
/// </summary>
/// <param name="cancellationToken">The cancellation token to observe.</param>
public CancellationTokenTaskSource(CancellationToken cancellationToken)
{
if (!cancellationToken.CanBeCanceled) {
Task = TaskConstants.Never;
return;
}
if (cancellationToken.IsCancellationRequested) {
Task = TaskConstants.Canceled;
return;
}
var tcs = new TaskCompletionSource();
_registration = cancellationToken.Register(() => tcs.TrySetCanceled(), false);
Task = tcs.Task;
}
private static AsyncCallback Callback(Action<IAsyncResult> endMethod, TaskCompletionSource<object> tcs)
{
return asyncResult => {
try {
endMethod(asyncResult);
tcs.TrySetResult(null);
}
catch (OperationCanceledException) {
tcs.TrySetCanceled();
}
catch (Exception ex) {
tcs.TrySetException(ex);
}
};
}