MVC Filter 返回json格式

        private void OnError(ActionExecutedContext filterContext)
        {
            string htmlMsg = @"<script type='text/javascript'>alert('系统出错了');</script>";
            var request = filterContext.RequestContext.HttpContext.Request;

            var result = new ContentResult
            {
                Content = htmlMsg,
                ContentType = "text/html",
            };
            if (request.IsAjaxRequest())
            {
                //filterContext.Result = new RedirectResult("/login");
                filterContext.Result = new JsonResult
                {
                    Data = new { ret = -998 },
                    ContentEncoding = System.Text.Encoding.UTF8,
                    ContentType = "application/json",
                    JsonRequestBehavior = JsonRequestBehavior.AllowGet
                };
            }
            else
                filterContext.Result = result;
        }