HttpClient setting boundary with content-type

Question

I am using javascript to communicate with a third party service. As part of their authentication process they need the \"multipart/form\" body of the post message including

Answer 1

I post my code here, maybe this will help anyone else struggling as I did, on my case this works and upload a file to my account (not a banking but a secure cloud file product)

 public  string UploadFile(string endpointUrl, string filePath, string accessToken)
    {

        FileStream fs = null;
        Stream rs = null;
        string result = "";
        try
        {

            string uploadFileName = System.IO.Path.GetFileName(filePath);

            fs = new FileStream(filePath, FileMode.Open, FileAccess.Read);

            var request = (HttpWebRequest)WebRequest.Create(endpointUrl);
            request.Method = WebRequestMethods.Http.Post;
            request.AllowWriteStreamBuffering = false;
            request.SendChunked = true;
            String CRLF = "\r\n"; // Line separator required by multipart/form-data.        
            long timestamp = DateTimeOffset.Now.ToUnixTimeSeconds();

            string boundary = timestamp.ToString("x");
            request.ContentType = "multipart/form-data; boundary=" + boundary;

            request.Headers.Add("Authorization", "Bearer " + accessToken);                             

            long bytesAvailable = fs.Length;
            long maxBufferSize = 1 * 1024 * 1024;


            rs = request.GetRequestStream();
            byte[] buffer = new byte[50];
            int read = 0;

            byte[] buf = Encoding.UTF8.GetBytes("--" + boundary + CRLF);
            rs.Write(buf, 0, buf.Length);

            buf = Encoding.UTF8.GetBytes("Content-Disposition: form-data; name=\"body\"; filename=\"" + uploadFileName + "\"" + CRLF);                
            rs.Write(buf, 0,buf.Length);

            buf = Encoding.UTF8.GetBytes("Content-Type: application/octet-stream;" + CRLF);
            rs.Write(buf, 0, buf.Length);

            buf = Encoding.UTF8.GetBytes(CRLF);
            //writer.append("Content-Type: application/octet-stream;").append(CRLF);
            rs.Write(buf, 0, buf.Length);
            rs.Flush();


            long bufferSize = Math.Min(bytesAvailable, maxBufferSize);
            buffer = new byte[bufferSize];
            while ((read = fs.Read(buffer, 0, buffer.Length)) != 0)
            {
                rs.Write(buffer, 0, read);
            }
            buf = Encoding.UTF8.GetBytes(CRLF);                
            rs.Write(buf, 0, buf.Length);
            rs.Flush();


            // End of multipart/form-data.
            buffer = Encoding.UTF8.GetBytes("--" + boundary + "--" + CRLF);
            rs.Write(buffer, 0, buffer.Length);

            using (var response = request.GetResponse())
            using (var responseStream = response.GetResponseStream())
            using (var reader = new StreamReader(responseStream))
            {

                result = reader.ReadToEnd();
            }
        }
        catch (Exception e)
        {
            result = e.InnerException != null ? e.InnerException.Message : e.Message;  
        }

        return result;
    }