I'm running a ASP.NET website on my development box (.NET 2.0 on Vista/IIS7). The Session_Start method in global.asax.cs logs every call to a file (log4net). The Session_End method also logs every call.

I'm using InProc session state, and set the session timeout to 5 mins (to avoid waiting for 20 mins).

I hit the website, wait for 5 minutes unit I see the Session_End logging. Then I F5 the website. The browsers still has the session cookie and sends it to the server. Session_Start is called and a new session is created using the same session id (btw: I need this to be the same session id, because it is used to store data in database).

Result: Every time I hit F5 on a previously ended session, the Session_Start method is called.

When I open a different browser, the Session_Start method is called just once. Then after 5 minutes the Session_End each F5 causes the Session_Start method to execute.

Can anyone explain why this is happening?

Update: After the Session timeout, all subsequent requests have a session start & session end. So in the end my question is: why are the sessions on these subsequent request closed immediatly?

2010-02-09 14:49:08,754 INFO  Global.asax[7486] [(null)] - Session started. SID=nzponumvf1hbaniverffp4mq host=127.0.0.1
2010-02-09 14:49:08,754 INFO  Global.asax[7486] [nzponumvf1hbaniverffp4mq] - Request start: GET http://localhost:80/js/settings.js
2010-02-09 14:49:08,756 INFO  Global.asax[7486] [(null)] - Session ended. SID=nzponumvf1hbaniverffp4mq
2010-02-09 14:49:08,760 INFO  Global.asax[7486] [(null)] - Session started. SID=nzponumvf1hbaniverffp4mq host=127.0.0.1
2010-02-09 14:49:08,760 INFO  Global.asax[7486] [nzponumvf1hbaniverffp4mq] - Request start: GET /css/package.aspx?name=core
2010-02-09 14:49:08,761 INFO  Global.asax[7486] [(null)] - Session ended. SID=nzponumvf1hbaniverffp4mq
2010-02-09 14:49:08,762 INFO  Global.asax[7486] [(null)] - Session started. SID=nzponumvf1hbaniverffp4mq host=127.0.0.1
2010-02-09 14:49:08,762 INFO  Global.asax[7486] [nzponumvf1hbaniverffp4mq] - Request start: GET /js/package.aspx?name=all
2010-02-09 14:49:08,763 INFO  Global.asax[7486] [(null)] - Session ended. SID=nzponumvf1hbaniverffp4mq
2010-02-09 14:49:08,763 INFO  Global.asax[7486] [(null)] - Session started. SID=nzponumvf1hbaniverffp4mq host=127.0.0.1
2010-02-09 14:49:08,763 INFO  Global.asax[7486] [nzponumvf1hbaniverffp4mq] - Request start: GET /css/package.aspx?name=rest
2010-02-09 14:49:08,764 INFO  Global.asax[7486] [(null)] - Session ended. SID=nzponumvf1hbaniverffp4mq
2010-02-09 14:49:08,764 INFO  Global.asax[7486] [(null)] - Session started. SID=nzponumvf1hbaniverffp4mq host=127.0.0.1
2010-02-09 14:49:08,765 INFO  Global.asax[7486] [nzponumvf1hbaniverffp4mq] - Request start: GET /css/package.aspx?name=vacation
2010-02-09 14:49:08,765 INFO  Global.asax[7486] [(null)] - Session ended. SID=nzponumvf1hbaniverffp4mq

web.config relevant section:

<system.web>
  <compilation debug="true" />
  <sessionState timeout="2" regenerateExpiredSessionId="false" />
</system.web>