Can a single asp.net user make more than one request at a time if the Session is in use?

Question

I am not able to make more than one request at a time in asp.net while the session is active. Why does this limitation exist? Is there a way to work around it?

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Answer 1

For reasons Kevin described, users can't access two pages that might write to their session state at the same time - the framework itself can't exert fine-grained control over the locking of the session store, so it has to lock it for entire requests.

To work around this, pages that only read session data can declare that they do so. ASP.NET won't obtain a session state write lock for them:

// Or false if it doesn't need access to session state at all
EnableSessionState="ReadOnly"

Answer 2

Here is a link talking about session state and locking. It does perform and exclusive lock.

The easiest way around this is to make the long running tasks asynchronous. You can make the long running tasks run on a separate thread, or use and asynchronous delegate and return a response to the browser immediately. The client side page can send requests to the server to check and see if it is done (through ajax most likely), and when the server tells the client it's finished, notify the user. That way although the server requests have to be handled one at a time by the server, it doesn't look like that to the user.

This does have it's own set of problems, and you'll have to make sure that account for the HTTP context closing as that will dispose certain functionality in the asp.net session. One example you'll probably have to account for is probably releasing a lock on the session, if that is actually occurring.

This isn't too surprising that this could be a limitation. Each browser would have it's own session, before the advent of ajax, post back requests were synchronous. Making the same session handle concurrent could get really ugly, and I can see how that wouldn't be a priority for the IIS and ASP.NET teams to add in.