All about Async/Await, System.Threading.Tasks, System.Collections.Concurrent, System.Linq, and more…
Every System.Threading.Tasks.Task instance goes through a lifecycle, and it only makes this journey once. To provide insight into where in that lifecycle a given Task is, the Task class provides an instance Status property. That property returns a value from the TaskStatus enumeration that reflects the current point in the lifecycle.
“Current” is the operative word here. Many of the states are transient, meaning that we’re dealing with a concurrent system, and by the time you’ve received the value of the status, the status may have changed. However, the lifecycle does not contain cycles (as ironic as that may sound), meaning that there’s a directionality to the various states, and once a given state has been reached, the Task won’t return back to that state again or to any that came before it. Additionally, there are three “final” states, where once in those states, the Task is no longer executing and will no longer change state.
Here are the states and an informal description of what they imply:
Several of these status values are also communicated through helper properties on the Task class. For a Task t:
Several operations in the Task Parallel Library are tied to the concept of a final state, or more generally to IsCompleted. For example, a call to the Wait method on a Task will not return until that Task’s IsCompleted is true. And the continuations for a Task will not fire until that same condition is met.