FaceBook Graph API - Reuse FaceBook same FaceBook Access Code and Token

Hi

I am using your code 

http://www.aspsnippets.com/Articles/Fetch-and-import-FaceBook-Friends-and-Contacts-with-profile-pictures-in-ASPNet.aspx

to get friend list from facebook it is working fine but i am facing the some issues to integrate it in my project

I have to first login from facebook to and verify the user if exist in application using FaceBookConnect.Fetch(code, "me"); then i call service to get frend list with same access code but it reutrn me 400 bad request error is there any way to solve this without reathunticate the user as i dont want to post back the page again to athunticate the user again