Newbie problem encountered regarding ASP.NET page life cycle

Hi I'm a ASP.NET newbie,
I have 2 custom control ascx files.  CompanyView.ascx and CompanyOperation.ascx where CompanyOperation is the subclass of the CompanyView (CompanyView contains CompanyOperation.ascx).

CompanyOpeartion.ascx will display company detail information base on the Session["id"], and Session["mode"].
        int companyID = -1;
        string mode = "";

        protected void Page_Load(object sender, EventArgs e)
        {
            if (Session["id"] == null || Session["mode"] == null)
                     // Handle Session Error
    &n ...