Friday, November 21, 2008

Background Processing Re-Revisited

OK, here’s the last word on this whole background processing / concurrency decorators thing. I went back and re-wrote the original decorators, but using the approach I used with the SyncContext version. I don’t want to rehash it again, here are the main points:

• Instead of using a property to retrieve the dispatcher, I get it via Application.Current.MainWindow.Dispatcher (checking to be sure Current and MainWindow aren’t null…err, None). This way, I pick up the dispatcher automatically rather than forcing a specific interface on the class with decorated methods. In fact, this approach should work with pure functions as well.
• Since I don’t have a convenient function like SetSynchronizationContext, I store the dispatcher in thread local storage for later use in calling back to the UI thread.
• Unlike the SyncContext version, this version propagates the return value of @UIThread decorated functions. I don’t propagate the return value of @BGThread functions – there’d be no point farming a task to a background thread then blocking the UI thread waiting for a response.

As usual, the code is on my SkyDrive. It includes both the SyncContext and Dispatcher version of the decorators.