Logout when Session Expires

[agarwalsunitadhn]

my problem is that after every 20minutes i got the error that the
Object reference not set to an instance of an object.
and highlight the line
lblWelcome.Text = "Welcome, " + Session["userName"].ToString();

I want that when the session expires either user will see LogIn page or the sesion resume their values.
Where i write the code for the above.... thanks for your code in advance

[kunal pawar]

Before use session checked that exists or not if not then redirect ur page to Login page

if Session["userName"] == null then response.redire ct('');

[agarwalsunitadhn]

Before use session checked that exists or not if not then redirect ur page to Login page

if Session["userName"] == null then response.redire ct('');

I have to record the logout time also. bt this code will not work it only to redirect to another page. becoze when the session expires then how i got the value that which user is logged in n how we record their time of logout in database

[kunal pawar]

Oh, then u need to maintain USer session in cookies or in hidden variable. that will help u to know which user's session expired

[agarwalsunitadhn]

Oh, then u need to maintain USer session in cookies or in hidden variable. that will help u to know which user's session expired

Thanks i had done that by storing the value in hidden field.

Thanks once again