Task.WaitAll Method (Task, CancellationToken)
Waits for all of the provided Task objects to complete execution.
Assembly: mscorlib (in mscorlib.dll)
The cancellationToken was canceled.
The tasks argument is null.
At least one of the Task instances was canceled -or- an exception was thrown during the execution of at least one of the Task instances. If a task was canceled, the AggregateException contains an in its InnerExceptions collection.
The tasks argument contains a null element.
One or more of the Task objects in tasks has been disposed.