public override void OnAddSession(HttpContext context)
        {
            DodoSession session = null;

            if (context.Request.Form["email"] != null)
            {
                session = CurrentDb.CheckEmail(
                    context.Request.Form["email"]);

                if (session == null)
                {
                    throw new Exception("Email is not correct");
                }
            }
            else
            {
                session = CurrentDb.CheckUserAndPwd(
                    context.Request.Form["user"], context.Request.Form["pwd"]);

                if (session == null)
                {
                    throw new Exception("User or Password is not correct");
                }
            }

            Sessions.AddSession(session);
            SetSessionState(context, session);
        }