An exception of type 'system.net.webexception' occurred in system.dll but was not handled in user code, server returned an error: (400) bad request

private static UploadedResponse PublishVideo(UploadResponse uploadResponse, string accessToken)
       {
           var request = WebRequest.Create("https://api.dailymotion.com/me/videos?url=" + HttpUtility.UrlEncode(uploadResponse.url));
           request.Method = "POST";
           request.ContentType = "application/x-www-form-urlencoded";
           request.Headers.Add("Authorization", "OAuth " + accessToken);

       var requestString = String.Format("title={0}&tags={1}&channel={2}&published={3}",
           HttpUtility.UrlEncode("Some new Title"),
           HttpUtility.UrlEncode("Tags"),
           HttpUtility.UrlEncode("news"),
           HttpUtility.UrlEncode("true"));

       var requestBytes = Encoding.UTF8.GetBytes(requestString);

       var requestStream = request.GetRequestStream();

       requestStream.Write(requestBytes, 0, requestBytes.Length);

       var response = request.GetResponse();

       var responseStream = response.GetResponseStream();
       string responseString;
       using (var reader = new StreamReader(responseStream))
       {
           responseString = reader.ReadToEnd();
       }

       var uploadedResponse = JsonConvert.DeserializeObject<UploadedResponse>(responseString);
       return uploadedResponse;
   }

var response = request.GetResponse();