启用 CORS 来解决这个问题（ajax跨域请求）

 1 <input type="file" name="btn_Upload" value="上传" id="btn_Upload" />
 2 <img src="" alt="" id="img_Upload" />
 3 
 4 @section Scripts
 5 {
 6     <link href="../../js/uploadifive-v1.2.2-standard/uploadifive.css" rel="stylesheet" />
 7     <script src="../../js/uploadifive-v1.2.2-standard/jquery.uploadifive.js"></script>
 8 }
 9 
10 <script>
11     $(function () {
12         $(‘#btn_Upload‘).uploadifive({
13             formData: { openId: ‘@ViewBag.OpenId‘ },
14             multi: false,
15             uploadScript: ‘@WXCommon.ConfigHelper.UploadUrl‘,
16             onUploadComplete: function (file, data) {
17                 if (data) {
18                     var json = $.parseJSON(data);
19                     if (json.res) {
20                         alert(json.msg);
21                         $(‘#img_Upload‘).attr({
22                             src: ‘@WXCommon.ConfigHelper.ThumbnailPath‘ + ‘/‘ + ‘@ViewBag.OpenId‘ + ‘/‘ + json.fileName
23                         });
24                     } else {
25                         alert(json.msg);
26                     }
27                 } else {
28                     alert(‘服务器内部错误!‘);
29                 }
30             }
31         });
32     });
33 </script>

 1 //独立部署的图片服务器
 2 public ActionResult Index()
 3 {
 4     //if (Request.HttpMethod == "OPTION")
 5     //{
 6     //    Response.AddHeader("Access-Control-Allow-Methods", "GET,POST");
 7     //    Response.AddHeader("Access-Control-Allow-Headers", "Content-Type,Accept");
 8     //    Response.AddHeader("Access-Control-Max-Age", "1728000");
 9     //    Response.AddHeader("Access-Control-Allow-Origin", "*");
10     //}
11     string openId = Request["openId"];
12     HttpPostedFileBase httpPostedFileBase = Request.Files["Filedata"];
13     string fileName = httpPostedFileBase.FileName;
14     string extensionName = System.IO.Path.GetExtension(fileName).ToLower();
15     if (extensionName == ".jpg" || extensionName == ".jpeg")
16     {
17         string virtualPath = "/uploads" + "/" + fileName.Replace(extensionName, "") + DateTime.Now.ToString("yyyyMMddhhmmss") + extensionName;
18         string fullPath = Server.MapPath(virtualPath);
19         httpPostedFileBase.SaveAs(fullPath);
20 
21         string savePath = Server.MapPath("/thumbnails" + "/" + openId);
22         string thumbnailFileName = Thumbnail.GetThumbnailImage(160, 120, fullPath, savePath, System.Drawing.Imaging.ImageFormat.Jpeg);
23         //删除原始文件
24         //System.IO.File.Delete(fullPath);
25         NowModel model = new NowModel();
26         model.Id = 0;
27         model.OpenId = openId;
28         model.FileName = thumbnailFileName;
29         nowBLL.Insert(model);
30         return Json(new { res = true, msg = "上传成功!", fileName = thumbnailFileName });
31     }
32     return Json(new { res = false, msg = "上传失败!" });
33 }

 1   <!--仅试用于IIS7以上版本，IIS6.0请用Response.AddHeader的方式-->
 2   <system.webServer>
 3     <validation validateIntegratedModeConfiguration="false" />
 4     <httpProtocol>
 5       <customHeaders>
 6         <add name="Access-Control-Allow-Origin" value="*"/>
 7         <add name="Access-Control-Allow-Methods" value="GET,POST,OPTION"/>
 8         <add name="Access-Control-Allow-Headers" value="Content-Type,soapaction"/>        
 9       </customHeaders>
10     </httpProtocol>
11   </system.webServer>