public static string vUserAgent
        {
            get
            {
                HttpContext context = HttpContext.Current;
                string ret = string.Empty;
                if (context != null)
                {
                    if (context.Session != null && context.Session["VisitorUserAgent"] != null)
                        ret = context.Session["VisitorUserAgent"].ToString();
                }
                return ret;
            }
            set { HttpContext.Current.Session["VisitorUserAgent"] = value.Trim(); }
        }