I have a site where the session needs to timeout because of security
concerns. I want to send the user back to the login page if the session is
expired.

Whats happening at the moment is that objects that exisit in the Session are
being accessed when the session has expired.
I know I could do an if Session["whatever"] != null or something similar to
detect whether the object is or isnt empty but there are many objects that
would need to be checked and I'll bet that some of them can be null quite
legitimately without needing the user to sign in again.

Question: Is there a way of doing something like:

if(Session.IsExpired){
// Redirect to login
}
else{
// Continue
}

Check the following

http://www.eggheadcafe.com/community/aspnet/17/10239034/sessions.aspx