how can i generate uniq session id in asp.net by changing in web.config

Question

i am creating Content management system in which i want to generate uniq session id i try it by changing in web.config part of sessionstate in which i put cookieless=true but when i try it it work good but pass sessionid with requested url which i do not want.please give solutin for it. also how can i destroy session id when application close.