Count of the number of active sessions?

Is it possible to find out the number of active sessions connected to your web application? Or do I have to keep my own count by incrementing in Session_Start() and decrementing in Session_End()?

I need to limit the number of sessions connecting at any one time...

I'm not sure about sessions, but if you're using the Membership class for logins, you can trap the number of users logged in with Membership.GetNumberOfUsersOnline().

On the global page you can store an object in application and everytime a session begins add one the the object and when the session ends subtract one from the object.