i want to clear session values when the browser is closed and update the status to logout in database

string strlogout = "logout";
          //updatelogouttime();
    //     public void updatelogouttime()
    //{
        Empbusinessaccesslayer obj = new Empbusinessaccesslayer();
        obj.Empname = Session["Username"].ToString();
        obj.Ipaddress = Session["ipaddress"].ToString();
        DateTime dt = (DateTime)Session["logintime"];
        obj.Createddate = Convert.ToDateTime(Session["logindate"].ToString());
        obj.Jobposteddate = dt;
        obj.Comptypeid = int.Parse(Session["comptypeid"].ToString());
        obj.Curremployer = strlogout;
        obj.updateuserlogout(Session["Username"].ToString(), Session["ipaddress"].ToString(), Convert.ToDateTime(Session["logindate"].ToString()), dt, int.Parse(Session["comptypeid"].ToString()), strlogout);

        Session["Username"] = null;
        Session["empname"] = null;
        Session["comptypeid"] = null;
        Session.Contents.Clear();
        Session.Abandon();