Async and await – difference between console, Windows Forms and ASP.NET

by

Since, in UI thread based application, the UI thread is always available (unless the process is stopped explicitly or by Windows), so the ThreadPool thread responsible for executing the code after “await” in any async method, will guarantee to find the UI thread to post the results back (if any).

This is slightly confused. There’s no indication that a ThreadPool thread will be required at all.

It’s up to the awaitable implementation to determine where to run the continuation, but normally the current synchronization context is used to work out where to run it:

  • In a console application, there is no synchronization context, so a thread pool thread is used for the continuation.
  • In a Windows Forms application, when you’re running on the UI thread the synchronization context is one which will execute code on the UI thread… so the continuation executes there (unless you use ConfigureAwait, etc…)
  • In an ASP.NET application, there’s a synchronization context specific to ASP.NET itself.

See Stephen Cleary’s MSDN article for more details.

It’s not clear what you mean by your later question about having to call Wait or Result in ASP.NET or a console app… in both scenarios it may be required, but equally it may not be. It depends on what you’re doing really. Don’t forget that even a console app can start its own threads and do all kinds of other things – you can write an HTTP server in a console app, for example…

More Related Contents:

  1. How and when to use ‘async’ and ‘await’
  2. If async-await doesn’t create any additional threads, then how does it make applications responsive?
  3. HttpClient.GetAsync(…) never returns when using await/async
  4. Should I avoid ‘async void’ event handlers?
  5. Running multiple async tasks and waiting for them all to complete
  6. How do yield and await implement flow of control in .NET?
  7. Fire and forget async method in asp.net mvc
  8. Task sequencing and re-entracy
  9. Enforce an async method to be called once
  10. Why use Async/await all the way down
  11. Different forms of the WCF service contract interface
  12. How does async works in C#?
  13. Why use async and return await, when you can return Task directly?
  14. Executing tasks in parallel
  15. Should I worry about “This async method lacks ‘await’ operators and will run synchronously” warning
  16. Proper way to start and fire-and-forget asynchronous calls?
  17. Use Task.Run() in synchronous method to avoid deadlock waiting on async method?
  18. A pattern for self-cancelling and restarting task
  19. Async always WaitingForActivation
  20. What is the correct way to cancel an async operation that doesn’t accept a CancellationToken?
  21. A pattern to pause/resume an async task?
  22. Async thread body loop, It just works, but how?
  23. Converting async/await to Task.ContinueWith
  24. Horrible performance using SqlCommand Async methods with large data
  25. How to Async Files.ReadAllLines and await for results?
  26. Async and Await with For Loop [duplicate]
  27. Await and SynchronizationContext in a managed component hosted by an unmanaged app
  28. When is the best place to use Task.Result instead of awaiting Task
  29. Timeout pattern on task-based asynchronous method in C#
  30. Synchronously waiting for an async operation, and why does Wait() freeze the program here

Leave a Comment