Accessing Session Variables at server side in asp.net -

client side

 <script type="text/javascript">     function getistektalebi(id) {         var istek2 = id;         '<%session["username"] = "'+istek2+'"; %>';          alert('<%=session["username"].tostring() %>');     }  </script> 

how can use session in server side in .cs asp.net

this code alow , working question

string val = httpcontext.current.session["deger"].tostring();