Task Status

One should always access tasks status in either try..catch statement or continued tasks

Created

Status Created is assigned when on task creation but usually seen on tasks created from constructors since other creation methods always start implicitly

Task task = new Task(() => { });
Console.WriteLine(task.Status); // Created

WaitingForActivation

WaitingForRun

A task has been scheduled by scheduler but has not yet begun execution

RanToCompletion

A task ran to end or terminated by return or ran to end has status RanToCompletion

Canceled

A successful cancellation happens when all of the three conditions were satisfied

• OperationCanceledException(or its derived exception type such as TaskCanceledException) is thrown
• token.IsCancellationRequested is true
• token in closure passed to OperationCanceledException equals token as parameter on task creation

There's a special case that can result in Canceled status when a task requires unwrap. If the inner task creation was Faulted because of a thrown of OperationCanceledException, the unwrap process would set the status of outer task to Canceled. Otherwise it would just remain Faulted.

// compiler would choose a Task.Run(Func<Task> function) here
var task = Task.Run(() => {
    throw new OperationCanceledException(); 
});

try {
    task.Wait();
} catch (AggregateException) {
    Console.WriteLine(task.Status); // Cancelled
}
// Explicit unwrap have the same behavior
// async was marked here because TaskFactory.StartNew does not have such overload resolution like Task.Run
Task task2 = Task.Factory.StartNew(async () => {
    await Task.Delay(100);
    throw new Exception(); // it's another type of Exception this time
}).Unwrap();

try {
    task2.Wait();
} catch (AggregateException) {
    Console.WriteLine(task2.Status); // Faulted
}

Faulted

Faulted happens on one of the scenarios:

• Any exception besides OperationCanceledException was thrown.
• OperationCanceledException is thrown but cancellation failed.
• Any exception is not OperationCanceledException was thrown on task creation. A wait on the task created anyway results Faulted.

Task task = Task.Factory.StartNew(() => {
    throw new Exception(); // not an OperationCanceledException
});

try {
    task.Wait();
} catch (AggregateException) {
    Console.WriteLine(task.Status); // Faulted
}