$阿贾克斯（{
                键入：POST，
                数据：FORMDATA，
                网址：/表格/ GetJobData
                数据类型：JSON，
                的contentType：假的，
                过程数据：假的，
                成功：函数（响应）{
                    如果（响应= NULL＆放大器;！＆安培; response.success）{
                        警报（response.responseText）;
                    }其他{
                        // DoSomethingElse（）
                        警报（response.responseText）;
                    }
                }，
                错误：功能（响应）{
                    警报（错误！）; //
                }            }）;
 

控制器：

  [HttpPost]
            公众的ActionResult GetJobData（乔布斯jobData）
            {              VAR mime类型= jobData.File.ContentType;
              VAR isFileSupported = AllowedMimeTypes（mime类型）;             如果（！isFileSupported）{
                     //错误
                    返回JSON（新{成功=假，responseText的=附加的文件不被支持。}，JsonRequestBehavior.AllowGet）;
             }
            其他
              {
                    //成功
                    返回JSON（新{成功= TRUE，responseText的=您的消息发送！}，JsonRequestBehavior.AllowGet）;
               }            }
 

I would like to control when to reply an error message and when a success message but I am always get the error message:

here is what I am trying to do:

 $.ajax({
                type: "POST",
                data: formData,
                url: "/Forms/GetJobData",
                dataType: 'json',
                contentType: false,
                processData: false,

                success: function (response) {                    
                   alert("success!") 
                },
                error: function (response) {
                   alert("error") // I'm always get this.
                }

            });

Controller:

         [HttpPost]
            public ActionResult GetJobData(Jobs jobData)
            {

              var mimeType = jobData.File.ContentType;
              var isFileSupported = AllowedMimeTypes(mimeType);

             if (!isFileSupported){        
                     //  Error
                    Response.StatusCode = (int)HttpStatusCode.BadRequest;
                    return Content("The attached file is not supported",               MediaTypeNames.Text.Plain);    
             }
            else
              {
                    //  Success
                    Response.StatusCode = (int)HttpStatusCode.OK;
                    return Content("Message sent!", MediaTypeNames.Text.Plain);     

               }   

            }

 $.ajax({
                type: "POST",
                data: formData,
                url: "/Forms/GetJobData",
                dataType: 'json',
                contentType: false,
                processData: false,               
                success: function (response) {
                    if (response != null && response.success) {
                        alert(response.responseText);
                    } else {
                        // DoSomethingElse()
                        alert(response.responseText);
                    }                          
                },
                error: function (response) {
                    alert("error!");  // 
                }

            });

Controller:

 [HttpPost]
            public ActionResult GetJobData(Jobs jobData)
            {

              var mimeType = jobData.File.ContentType;
              var isFileSupported = AllowedMimeTypes(mimeType);

             if (!isFileSupported){        
                     //  Error
                    return Json(new { success = false, responseText = "The attached file is not supported." }, JsonRequestBehavior.AllowGet);
             }
            else
              {
                    //  Success
                    return Json(new { success = true, responseText= "Your message successfuly sent!"}, JsonRequestBehavior.AllowGet);
               }   

            }