ASP.NET global events

Question

which event is the most suitable to check for Session expired? i'm trying to trap each server request, and if Session is null, redirect to a different page.

Answer 1

This is often best achieved by using a base Page class for all otehr classes, and implementing this in the Page_Load method.

Answer 2

You can determine if a new session is being created by hooking Session_OnStart - http://msdn.microsoft.com/en-us/library/ms178583(VS.80).aspx

You can handle the Session_OnStart event by adding a subroutine named Session_OnStart to the Global.asax file. The Session_OnStart subroutine is run at the beginning of a request if the request begins a new session. A new session will be started if a request is made that does not contain a SessionID value or if the SessionID property contained in the request references a session that has expired.

This will tell you effectively when a new session is being created, regardless of if the user just arrived or the session had expired.

It would be hard to reliably differentiate between both scenarios. I guess you could try to get a hold a the session id in the either the session cookie or embedded in the url (cookieless), but you would need to check it before getting to the above event, and later check whether the request had a session id originally. Check if you can get to the session id in the cookieless version, because it is stripped out of the urls asp.net gives you (not sure if early in the lifecycle you get to see it).

Answer 3

Use BasePage class, which inherits from Page class. Let every aspx page inherits that BasePage class. In BasePage class, override OnInit event, in which you can check for Session or Cookie, and redirect user to login page (for example).
I use this approach for all mine webforms apps, because it's easy to implement and use.