ashx,中返回类型设置成 json,plain时，返回的Json代码解析都出错，调试发现实际返回的除了json字符串外还有，其他html或xml导致无法解析成json对象

function UploadFile(elmFlag) {            $.ajaxFileUpload({                url: '/FileUpload.ashx',                secureuri: false,                fileElementId: "fu" + elmFlag,                dataType: "json",                success: function (data, status) {                    if (data.Code == 200) {                        alert( unescape(data.Name));                    } else {                        alert( unescape(data.Msg));                    }                    $("#c_" + elmFlag).empty();                    $("#c_" + elmFlag).append("");                },                error: function (data, status, e) {                    alert("错误：上传组件错误，请检察网络!");                }            });        }

 服务器端

using System;using System.Collections.Generic;using System.Linq;using System.Web;using System.Web.Script.Serialization;using System.IO;using System.Web.Hosting;using F.Studio.Common;using Microsoft.Practices.Unity;using JLMFG.Doc.BLL;using JLMFG.Doc.Domain;namespace JLMFG.Doc.Web{    /// 
    /// FileUpload 的摘要说明    /// 
    public class FileUpload : IHttpHandler,IBuildUp    {        static readonly string C_FileRoot = "/Files/";        [Dependency]        public doc_DocManager DocMgr { get; set; }        private HttpRequest Request { get;  set; }        private HttpResponse Response { get; set; }        private JavaScriptSerializer Serializer { get; set; }        public void ProcessRequest(HttpContext context)        {            Request = context.Request;            Response = context.Response;            Serializer = new JavaScriptSerializer();            Response.ContentType = "text/html";            Response.Expires = -1;            try            {                if (Request.Files.Count <= 0) throw new Exception("没有文件上传!");                             SaveFile();            }            catch (Exception ex)            {                var resp=new UploadResponse(){Code=400,Msg=StringHelper.Escape(ex.Message)};                Response.Write(Serializer.Serialize(resp));            }            Response.End();                   }        private void  SaveFile()        {            var file = Request.Files[0];            var ext = Path.GetExtension(file.FileName);            //确保目录存在            string path =  C_FileRoot + DateTime.Now.ToString("yyyy-MM-dd") + "/";            if (!Directory.Exists( HostingEnvironment.MapPath(path)))            {                Directory.CreateDirectory(HostingEnvironment.MapPath(path));            }            //合成文件名            var filename= path + Guid.NewGuid().ToString("N").Substring(0,8) + ext;            var resp = new UploadResponse();            resp.MIME = file.ContentType;            resp.Size = file.ContentLength / 1024;            resp.Name =StringHelper.Escape( Path.GetFileNameWithoutExtension(file.FileName));            resp.Path =StringHelper.Escape( filename);            resp.Code = 200;            resp.Msg = "Success";            //保持文件            file.SaveAs(System.Web.Hosting.HostingEnvironment.MapPath(filename));                 Response.Write(Serializer.Serialize(resp));        }        public bool IsReusable        {            get            {                return false;            }        }        public class UploadResponse        {            public int Code { get; set; }            public string Msg { get; set; }            public string Path { get; set; }            public string Name { get; set; }            public long Size { get; set; }            public string MIME { get; set; }        }    }}