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!!! */ });

在Chrome中

标题

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

响应

[{“Name”:”Nome”,”ErrorMessage”:”campo obrigatório.”}]

在铬中工作！

在IE8中

标题(请求)

POST /Motivos/Salvar HTTP/1.1
Accept: application/json,*/*; 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

标题(响应)

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

不行！！

Asp.net MVC

过滤

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);
        }
    }
}

应用于GlobalFilterCollection

控制器

[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);
}

延伸

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;
}

问题

>为什么没有xhr.resposeText对象？
>如何以与Chrome恢复相同的方式检索JSON？

我需要JSON来填写表单！

注意：03/11/2014

当我添加Response.TrySkipIisCustomErrors = true;在我的控制器，它的作品！
responseText返回的是json。
为什么？