ASP.NET Session_End called immediately after Session_Start after a session timeout

Question

I have handlers for my Session_Start and Session_End events. When I first start the application, everything works fine. If I leave the session and the standard timeout occurs, I watch my Session_End throw. I'm expecting that behavior.

Let's say though, I come back after the timeout and refresh a page. The Session_Start method runs, but then immediately the Session_End method runs. I'm expecting another 15 minutes of idleness between Session_Start and Session_End.

What would be the problem?

EDIT: Yes, same session id.

EDIT 2: Cookies look like they are supposed to expire at the end of session. Not sure why I keep getting this loop of Session_Start/Session_End. I've also tried calling Session.Abandon() from Session_End, and that didn't work. This is running off the ASP.NET Development server too. I haven't tried it on a real IIS server yet.

Answer 1

Can you verify that the events are firing for the same session ID?

Answer 2

.Net does some funky things with their session cookies, esp. in conjunction with Forms auth. I'm just guessing, but I'd think that the client is hanging on to the cookie, and re-sending it to the server even after its invalid, which (I'm guessing here) might trigger a restart of the session, at which point it recognizes that its invalid and trashes it, causing the session end.

Try:

1. Making sure your cookies are set to expire properly
2. Calling Session.Abandon() and FormsAuthentication.SignOut()

Not sure if that helps, but FWIW.

Answer 3

It's a bit late to answer but it might be useful to other users who have the same problem.. I've experienced the same behavior as you've seen: Session_Start() and Session_End() are called for every request after the first timeout and the SessionID is always the same:

1. I've run the same code with ASP.NET 4.0 and the problem is gone.

2. As a workaround in ASP.NET 2.0/3.5, just put anything in the session collection (Session["dummy"] = "dummy"), and Session_Start() and Session_End() will behave normally.