Checking if the user is logged in my class

 Hi Guys,
right now in the project i'm working, we are checking if the user is logged inside every aspx page. I know it's wrong and i want to know how can i intercept the requests after authentication when i already have access to the SESSION variable and check  if the user is logged. If he is logged i redirect him to the requested page.
 
Thank you,
Jaq 
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