How to use non-thread-safe async/await APIs and patterns with ASP.NET Web API?

by

Entity Framework will (should) handle thread jumps across await points just fine; if it doesn’t, then that’s a bug in EF. OTOH, OperationContextScope is based on TLS and is not await-safe.

1. Synchronous APIs maintain your ASP.NET context; this includes things such as user identity and culture that are often important during processing. Also, a number of ASP.NET APIs assume they are running on an actual ASP.NET context (I don’t mean just using HttpContext.Current; I mean actually assuming that SynchronizationContext.Current is an instance of AspNetSynchronizationContext).

2-3. I have used my own single-threaded context nested directly within the ASP.NET context, in attempts to get async MVC child actions working without having to duplicate code. However, not only do you lose the scalability benefits (for that part of the request, at least), you also run into the ASP.NET APIs assuming that they’re running on an ASP.NET context.

So, I have never used this approach in production. I just end up using the synchronous APIs when necessary.

More Related Contents:

  1. Awaiting multiple Tasks with different results
  2. Running multiple async tasks and waiting for them all to complete
  3. Using async/await for multiple tasks
  4. Calling async method synchronously
  5. Fire and forget async method in asp.net mvc
  6. StaTaskScheduler and STA thread message pumping
  7. Run async method regularly with specified interval
  8. TAP global exception handler
  9. Why should I prefer single ‘await Task.WhenAll’ over multiple awaits?
  10. Regarding usage of Task.Start() , Task.Run() and Task.Factory.StartNew()
  11. Task sequencing and re-entracy
  12. Is there anything like asynchronous BlockingCollection?
  13. Cancelling a pending task synchronously on the UI thread
  14. Pattern for calling WCF service using async/await
  15. Waiting for async/await inside a task
  16. Revisiting Task.ConfigureAwait(continueOnCapturedContext: false)
  17. ConfigureAwait pushes the continuation to a pool thread
  18. How can I prevent synchronous continuations on a Task?
  19. If my interface must return Task what is the best way to have a no-operation implementation?
  20. multiple awaits vs Task.WaitAll – equivalent?
  21. Executing tasks in parallel
  22. Difference between returning and awaiting a Task in an async method [duplicate]
  23. Use Task.Run() in synchronous method to avoid deadlock waiting on async method?
  24. A pattern for self-cancelling and restarting task
  25. How to correctly write Parallel.For with async methods
  26. What is the correct way to cancel an async operation that doesn’t accept a CancellationToken?
  27. Converting async/await to Task.ContinueWith
  28. The lack of non-capturing Task.Yield forces me to use Task.Run, why follow that?
  29. How do I get a return value from Task.WaitAll() in a console app?
  30. Create a completed Task

Leave a Comment