Check for Session in Asp.Net

Question

Hi All, 

        May be this is a silly Question, How to check These two conditions , 

        1.The session is not expired but , the session variable is not assigned any value.

        2. Session variable is assigned with value, but session is expired.

        if(Session["mykey"] != null)

       {

        // Session is not expired

        }

        else

       {

          // Session is expired

        }

    Will this condition work for above two scenarios, or do i have to handle this both differently.

Please Help.