Open a pop up that states that the sessions has expired and redirect the user to the default login page

I want the solution of following problem in asp.net:

1. Open a pop up that states that the sessions has expired and redirect the user to the default login page.

OR

1. open a pop up that states that the sessions has expired, prompt for user credentials and after successfully authenticating, redirect the u开发者_运维技巧ser to the page they were originally requesting to view. If authentication is not successful after three tries, redirect them to the default login page with a message stating that they were not authenticated. Additionally, how should i extend the existing time out values of session to accommodate lengthy queries?

You could create a heartbeat AJAX call to the server (make sure that it doesn't use the session) every 30secs or so.