how to restrict user from accessing page in asp

in my project, there is two folders 1- user folders, 2-Admin folders. in users folders i have web pages for users and in the admin folders i have web pages for the admin. i have created two role, one is users and second is administrator. now i want only the person with administrator role can access the web pages which is admin folder. when user try to access the pages which is admin folders then it redirected to an error page.