Setting Thread.CurrentPrincipal with async/await

Question

Below is a simplified version of where I am trying to set Thread.CurrentPrincipal within an async method to a custom UserPrincipal object but the custom object is getting lo

Answer 1

The Thread.CurrentPrincipal is stored in the ExecutionContext which is stored in the Thread Local Storage.

When executing a delegate on another thread (with Task.Run or ThreadPool.QueueWorkItem) the ExecutionContext is captured from the current thread and the delegate is wrapped in ExecutionContext.Run. So if you set the CurrentPrincipal before calling Task.Run, it would still be set inside the Delegate.

Now your problem is that you change the CurrentPrincipal inside Task.Run and the ExecutionContext is only flowed one way. I think this is the expected behavior in most case, a solution would be to set the CurrentPrincipal at the start.

What you originally want is not possible when changing the ExecutionContext inside a Task, because Task.ContinueWith capture the ExecutionContext too. To do it you would have to capture somehow the ExecutionContext right after the Delegate is ran and then flowing it back in a custom awaiter's continuation, but that would be very evil.