最新版微信PC端小程序不能上传图片，服务器端收不到文件请求，请问怎么解决?

  wx.uploadFile({

            url: app.data.domain + '/api/File/UploadFromForm',

            filePath: res.tempFilePaths[i],

            name: 'uploadfile_ant',

            formData: {

              'SessionKey': app.data.shopssessionKey

            },

            header: {

              "Content-Type": "multipart/form-data"

            },

            success: function (response) {

服务器端 asp.net api

  HttpContextBase context = (HttpContextBase)Request.Properties["MS_HttpContext"];//获取传统context

            HttpRequestBase request = context.Request;

            if (!CheckShopsSession(request.Form["SessionKey"]))

            {

            }

            HttpPostedFileBase httpPostedFileBase = request.Files["uploadfile_ant"];