invoke ibm watson discovery adddocument api using httpwebrequest

Question

i need to integrate watson discovery features into existing windows service application developed with visual studio 2015 framework 4.5.

we cannot upgrade the framework version, so nuget library ibm.watson is not working.

i try to convert this curl command

curl -X POST -u "{username}":"{password}" -F "file=@c:\temp\1.json" https://gateway-fra.watsonplatform.net/discovery/api/v1/environments/{environment}/collections/{collection}/documents?version=2017-11-07

into c# code:

  void test
    {

        ServicePointManager.Expect100Continue = true;
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

        string username = "{username}";
        string password = "{password}";
        string postData = File.ReadAllText(@"c:\temp\1.json");

        string BASE_URL = "https://gateway-fra.watsonplatform.net/discovery/api/";
        string url = BASE_URL + "/v1/environments/{environment}/collections/{collection}/documents";

        var request = (HttpWebRequest)WebRequest.Create(url);

        var data = Encoding.ASCII.GetBytes(postData);

        request.Method = "POST";
        request.ContentType = "application/json";
        request.ContentLength = data.Length;
        request.Credentials = new NetworkCredential(username, password);

        using (var stream = request.GetRequestStream())
        {
            stream.Write(data, 0, data.Length);
        }

        var response = (HttpWebResponse)request.GetResponse();

        var responseString = new  StreamReader(response.GetResponseStream()).ReadToEnd();
 catch (WebException wex)
            {
                HttpWebResponse oHttpWebResponse = (HttpWebResponse)wex.Response;

                Encoding oEncoding = Encoding.GetEncoding(1252);
                string sEx = string.Empty;
                using (StreamReader oStreamReader = new StreamReader(oHttpWebResponse.GetResponseStream(), oEncoding))
                {
                    sEx = oStreamReader.ReadToEnd();
                    oStreamReader.Close();
                }
                System.Diagnostics.Debug.WriteLine(sEx);
            }
            catch (Exception ex)
            {
                System.Diagnostics.Debug.WriteLine(ex.ToString());
            }
}

but get this error:

{
  "code": 400,
  "error": "The request does not contain a \"file\" part or \"metadata\" part. Include at least one of those parts and resubmit your request."
}

what's the way to add file or metadata to request?

Answer 1

this worked for me:

async Task<string> Upload()
        {
            string environmentId = "xxx";
            string collectionId = "xxx";
            string username = "xxx";
            string password = "xxx";
            string sResult = string.Empty;
            string filename = @"c:\temp\watson\2824.json";
            string url = $"https://gateway-fra.watsonplatform.net/discovery/api/v1/environments/{environmentId}/collections/{collectionId}/documents?version=2018-08-01";
            FileStream fileStream = new FileStream(filename, FileMode.Open);
            HttpContent fileStreamContent = new StreamContent(fileStream);
            var credentials = new NetworkCredential(username, password);
            var handler = new HttpClientHandler { Credentials = credentials };
            using (var client = new HttpClient(handler))
            {
                using (var formData = new MultipartFormDataContent())
                {
                    formData.Add(fileStreamContent, "file", filename);
                    var response = await client.PostAsync(url, formData);
                    if (response.IsSuccessStatusCode)
                    {
                        Stream oStream = await response.Content.ReadAsStreamAsync();
                        using (var reader = new StreamReader(oStream))
                        {
                            sResult = reader.ReadToEnd();
                            reader.Close();
                        }
                    }
                }
            }
            fileStream.Close();
            return sResult;
        }