HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
            req.AllowWriteStreamBuffering = false;
            req.Method = WebRequestMethods.Http.Post;
            req.ContentType = "multipart/form-data; boundary=" + boundaryString;
            req.KeepAlive = false;
            req.ContentLength = getMultiPartReqLen(boundaryString, files, data);