ASP.Net Asynchronous HTTP File Upload Handler

Question

I\'m trying to make a file upload handler in C# that is asynchronous and can provide updates on progress of the file through AJAX asynchronous requests. Basically if the request

Answer 1

I assume you're using the default ASP.Net Session manager and I see that you call GetSessionStore to get your session. Unfortunately the default Session manager serializes all requests when a call requires write access to the Session Store. This StackOverflow question and this MSDN arcle on Session State have some very useful information on Session State and it's locking behaviors.

Now, To take care of your problem, you're going to have to do a couple things which depend on whether you're using MVC controllers or if you're writing a custom IHttpHandler.

• If you're writing your own IHttpHandler, make sure you do not have the IRequiresSessionState or IReadOnlySessionState interfaces added to your handler. In doing so, the pipeline will skip looking for a session and go straight to processing. context.Session will be null in this situation.
• If you're using MVC to process the request, you'll need to decorate your controller class with the SessionState attribute passing in the SessionStateBehavior of SessionStateBehavior.Disabled.

In either case you won't be able to rely on the Session object to store your upload statuses. You can create a static ConcurrentDictionary keyed off of their SessionID (which you'll either need to pass in the upload query string or read the cookie yourself, calling Session.SessionId will just block you again) and store your upload statuses in there (which look like they're Concurrent* as well).

Another option would be to replace the SessionStateProvider with your own custom provider but that might be overkill in this situation.