public JsonResult _Login(LoginModel loginModel)
        {
            ///
            /// NOTE: This is where your logic goes
            /// 

            //for testing           
            if (ModelState.IsValid)
            {
                if (loginModel.IsValidUser(loginModel.Login, loginModel.Password))
                {
                    Session["user"] = new LoginModel() {Login = loginModel.Login};
                    return Json(JsonResponseFactory.SuccessResponse(), JsonRequestBehavior.DenyGet);
                }
                else
                {
                    ModelState.AddModelError("", "Błędne dane logowania.");
                    return Json(JsonResponseFactory.ErrorResponse("Błędne dane logowania."), JsonRequestBehavior.DenyGet);
                }
            }
            else
            {
                return Json(JsonResponseFactory.ErrorResponse(""), JsonRequestBehavior.DenyGet);
            }
        }
        public JsonResult _Login(LoginModel model)
        {
            ///
            /// NOTE: This is where your logic goes
            /// 

            //for testing           
            if (model.UserName == "fail")
            {
                return Json(JsonResponseFactory.ErrorResponse("You told me to fail."), JsonRequestBehavior.DenyGet);
            }
            else
            {
                return Json(JsonResponseFactory.SuccessResponse(), JsonRequestBehavior.DenyGet);
            }
        }