Pls Help, i have a problem loading my gridview with data

[atplerry]

Hello
i have problem loading my gridview with data if i include a where clause to it to pull out records using either session or querystring but without a query string it will retrieve out information but i have been working on this for days but no solution your concern will be appreciated.
Moreso, i have a site that when use login i want login user information only to be retrieve throughout the site i thought of using session OR querystring but for security purpose i am scared of using either the two. What suggestion are you giving me to help me with this. What other method can i use to maintain state which will be secured.
Thanks