/// <summary>
/// Attempts to transition the underlying
/// <see cref="T:System.Threading.Tasks.Task{TResult}"/> into the
/// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>
/// state.
/// </summary>
/// <returns>True if the operation was successful; otherwise, false.</returns>
/// <remarks>This operation will return false if the
/// <see cref="T:System.Threading.Tasks.Task{TResult}"/> is already in one
/// of the three final states:
/// <see cref="System.Threading.Tasks.TaskStatus.RanToCompletion">RanToCompletion</see>,
/// <see cref="System.Threading.Tasks.TaskStatus.Faulted">Faulted</see>, or
/// <see cref="System.Threading.Tasks.TaskStatus.Canceled">Canceled</see>.
/// </remarks>
/// <exception cref="T:System.ObjectDisposedException">The <see cref="Task"/> was disposed.</exception>
public bool TrySetCanceled()
{
bool returnValue = false;
// "Reserve" the completion for this task, while making sure that: (1) No prior reservation
// has been made, (2) The result has not already been set, (3) An exception has not previously
// been recorded, and (4) Cancellation has not been requested.
//
// If the reservation is successful, then record the cancellation and finish completion processing.
//
// Note: I had to access static Task variables through Task<object>
// instead of Task, because I have a property named Task and that
// was confusing the compiler.
if (m_task.AtomicStateUpdate(Task <object> .TASK_STATE_COMPLETION_RESERVED,
Task <object> .TASK_STATE_COMPLETION_RESERVED | Task <object> .TASK_STATE_CANCELED |
Task <object> .TASK_STATE_FAULTED | Task <object> .TASK_STATE_RAN_TO_COMPLETION))
{
m_task.RecordInternalCancellationRequest(); // record the request
m_task.CancellationCleanupLogic(); // perform cancellation cleanup actions
returnValue = true;
}
else if (!m_task.IsCompleted)
{
// The only way that m_task is not completed is if it is in a COMPLETION_RESERVED state.
// Just wait a bit until the completion is finalized.
SpinWait sw = new SpinWait();
while (!m_task.IsCompleted)
{
sw.SpinOnce();
}
}
return(returnValue);
}
