public static async Task<String> UploadFile(string apiURL, string accessToken, string filePath)
        {
            String result = String.Empty;
            using (var client = new HttpClient())
            {
                client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
                using (var content = new MultipartFormDataContent())
                {
                    HttpContent stringContent = new StringContent(Path.GetFileNameWithoutExtension(filePath));
                    content.Add(stringContent, "filename", Path.GetFileNameWithoutExtension(filePath));

                    var fileContent = new ByteArrayContent(System.IO.File.ReadAllBytes(filePath));
                    fileContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data")
                    {
                        Name = "file",
                        FileName = Path.GetFileName(filePath)
                    };
                    content.Add(fileContent);

                    try
                    {
                        HttpResponseMessage response = await client.PostAsync(apiURL, content);
                        response.EnsureSuccessStatusCode();
                        
                        // equivalent of pressing the submit button on the form 
                        if (response.IsSuccessStatusCode)
                            result = response.Content.ReadAsStringAsync().Result;
                    }
                    catch (Exception ex)
                    {
                        throw ex;
                    }
                }
            }
            return result;
        }