restrict direct access from user to aspx page

 Hi  I am a newbie in asp.net circumstances.
Is there any way which I prohibit all user from access *.aspx pages directly.  I will make one page as distributor
That page will check valid token and parameters . After checking validation , request will be redirected the specific aspx page
I like to process the request redirected from distributor page. Maybe I can  check session value or etc. 
Is there any function which tells the web request is redirected from specific page.
Thanks in advance.
With Regards,
Park  
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