Twitter Image Upload (not working)

byte[] bytearray = File.ReadAllBytes(filename);
            string media_data = Convert.ToBase64String(bytearray);

            var oauth_version = "1.0";
            var oauth_signature_method = "HMAC-SHA1";
            var oauth_nonce = Convert.ToBase64String(
                                              new ASCIIEncoding().GetBytes(
                                                   DateTime.Now.Ticks.ToString()));
            var timeSpan = DateTime.UtcNow
                                              - new DateTime(1970, 1, 1, 0, 0, 0, 0,
                                                   DateTimeKind.Utc);
            var oauth_timestamp = Convert.ToInt64(timeSpan.TotalSeconds).ToString();
            var resource_url = "https://upload.twitter.com/1.1/media/upload.json";

            /*var baseFormat = "media_data={0}&oauth_consumer_key={1}&oauth_nonce={2}&oauth_signature_method={3}" +
            "&oauth_timestamp={4}&oauth_token={5}&oauth_version={6}";*/

            var baseFormat = "oauth_consumer_key={0}&oauth_nonce={1}&oauth_signature_method={2}" +
            "&oauth_timestamp={3}&oauth_token={4}&oauth_version={5}";

            var baseString = string.Format(baseFormat,
                                        //media_data,
                                        oauth_consumer_key,
                                        oauth_nonce,
                                        oauth_signature_method,
                                        oauth_timestamp,
                                        oauth_token,
                                        oauth_version//,
                                        //Uri.EscapeDataString(status)
                                        );

            baseString = string.Concat("POST&", Uri.EscapeDataString(resource_url),
                         "&", Uri.EscapeDataString(baseString));

            Console.WriteLine(baseString);

            var compositeKey = string.Concat(Uri.EscapeDataString(oauth_consumer_secret),
                    "&", Uri.EscapeDataString(oauth_token_secret));

            string oauth_signature;
            using (HMACSHA1 hasher = new HMACSHA1(ASCIIEncoding.ASCII.GetBytes(compositeKey)))
            {
                oauth_signature = Convert.ToBase64String(
                    hasher.ComputeHash(ASCIIEncoding.ASCII.GetBytes(baseString)));
            }

            var headerFormat = "OAuth oauth_consumer_key=\"{0}\", oauth_nonce=\"{1}\", " +
               "oauth_signature=\"{2}\", oauth_signature_method=\"{3}\", " +
               "oauth_timestamp=\"{4}\", oauth_token=\"{5}\", " +
               "oauth_version=\"{6}\"";

            var authHeader = string.Format(headerFormat,
                                    Uri.EscapeDataString(oauth_consumer_key),
                                    Uri.EscapeDataString(oauth_nonce),
                                    Uri.EscapeDataString(oauth_signature),
                                    Uri.EscapeDataString(oauth_signature_method),
                                    Uri.EscapeDataString(oauth_timestamp),
                                    Uri.EscapeDataString(oauth_token),
                                    Uri.EscapeDataString(oauth_version)
                            );

            Console.WriteLine(authHeader);

            var postBody = "media_data=" + Convert.ToBase64String(bytearray);

            ServicePointManager.Expect100Continue = false;

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(resource_url);
            request.Headers.Add("Authorization", authHeader);
            request.Method = "POST";
            request.ContentType = "multipart/form-data";
            using (Stream stream = request.GetRequestStream())
            {
                byte[] content = ASCIIEncoding.ASCII.GetBytes(postBody);
                stream.Write(content, 0, content.Length);
            }

            WebResponse response = request.GetResponse();
            Console.WriteLine(((HttpWebResponse)response).StatusDescription);
            Stream dataStream = response.GetResponseStream();
            StreamReader reader = new StreamReader(dataStream);
            string responseFromServer = reader.ReadToEnd();
            Console.WriteLine(responseFromServer);