When performing post via ajax, Bad Request is returned instead of the JSON result

Javascript ``` jqXHR = $.ajax({ url: $frm.attr("action"), type: "POST", dataType: "json", cache: false, headers: headers, contentType: "application/json;charset=UTF-8", data: ko.mapping.toJSON(data, map), beforeSend: function(x) { if (x && x.overrideMimeType) { return x.overrideMimeType("application/json;charset=UTF-8"); } } }); jqXHR.fail(function(xhr, err, msg) { /* xhr.responseText NEED TO BE JSON!!! */ }); ``` In Chrome Headers ``` Request Method:POST Status Code:400 Bad Request Request Headersview source Accept:application/json, text/javascript, */*; q=0.01 Accept-Encoding:gzip,deflate,sdch Accept-Language:en-US,en;q=0.8,pt-BR;q=0.6,pt;q=0.4 Connection:keep-alive Content-Length:10 Content-Type:application/json;charset=UTF-8 User-Agent:Mozilla/5.0 (Windows NT 6.3; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/33.0.1750.117 Safari/537.36 X-Requested-With:XMLHttpRequest Request Payloadview source {Id:0} Response Headersview source Cache-Control:private Content-Length:54 Content-Type:application/json; charset=utf-8 Date:Thu, 27 Feb 2014 14:01:59 GMT Server:Microsoft-IIS/8.0 X-AspNet-Version:4.0.30319 X-AspNetMvc-Version:5.1 X-Powered-By:ASP.NET ``` Response [{"Name":"Nome","ErrorMessage":"campo obrigatório."}] Works in chrome! In IE8 Headers (Request) ``` POST /Motivos/Salvar HTTP/1.1 Accept: application/json, text/javascript, */*; q=0.01 Accept-Language: pt-br x-requested-with: XMLHttpRequest Content-Type: application/json;charset=UTF-8 Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0) Content-Length: 10 Connection: Keep-Alive Pragma: no-cache ``` Headers (Response) ``` HTTP/1.1 400 Bad Request Cache-Control: private Content-Type: text/html Server: Microsoft-IIS/8.0 X-AspNetMvc-Version: 5.1 X-AspNet-Version: 4.0.30319 X-Powered-By: ASP.NET Date: Thu, 27 Feb 2014 13:51:46 GMT Content-Length: 11 Bad Request ``` NOT WORK!! Asp.net MVC Filter ``` public class HandleExceptionAttribute : HandleErrorAttribute { public override void OnException(ExceptionContext filterContext) { if (filterContext.HttpContext.Request.IsAjaxRequest() && filterContext.Exception != null) { filterContext.HttpContext.Response.StatusCode = (int)HttpStatusCode.InternalServerError; var ex = filterContext.Exception.GetBaseException(); filterContext.Result = new JsonResult { JsonRequestBehavior = JsonRequestBehavior.AllowGet, Data = new { ex.Message, ex.GetType().Name } }; filterContext.ExceptionHandled = true; } else { base.OnException(filterContext); } } } ``` Apply on GlobalFilterCollection Controller ``` [ValidateJsonAntiForgeryToken, HttpPost] public virtual JsonResult Salvar(TViewModel viewModel) { if (ModelState.IsValid) { TEntity model; if (default(TKey).Equals(viewModel.Id)) { model = Mapper.Map<TEntity>(viewModel); AdicionarEntidade(model, viewModel); } else { model = Repositorio.Get(viewModel.Id); Mapper.Map(viewModel, model, typeof(TViewModel), typeof(TEntity)); SalvarEntidade(model, viewModel); } return SalvarResult(model); } Response.StatusCode = 400; return Json(ModelState.ToJson(), JsonRequestBehavior.AllowGet); } ``` Extenssion ``` public static object ToJson(this ModelStateDictionary dic, params string[] othersMessages) { var states = (from e in dic where e.Value.Errors.Count > 0 select new { Name = e.Key, e.Value.Errors[0].ErrorMessage }).ToList(); if (othersMessages != null) foreach (var message in othersMessages) states.Add(new { Name = "", ErrorMessage = message }); return states; } ``` Questions - Why not have the xhr.resposeText object? - How to retrieve JSON in the same way that I recover in Chrome? I need the JSON to populate the form! Notes: 03/11/2014 When I add `Response.TrySkipIisCustomErrors = true;` in my controler, it works! responseText returns the json. Why?