using System.Net.Http;
using System.Text;
            
  private async void Post20()
        {
            HttpClient client = new HttpClient();
            //string json = "{\"id\":\"12\"}";//JsonConvert.SerializeObject(values);
            string json = txtObject.Text;
            StringContent content = new StringContent(json.ToString(), Encoding.UTF8, "application/json");
            HttpResponseMessage httpResponse = client.PostAsync(txtUrl.Text, content).Result;

            var responseString = await httpResponse.Content.ReadAsStringAsync();
            txtResponse.Text = responseString;
        }

 public boolean checkNetworkConnection() {
        ConnectivityManager connMgr = (ConnectivityManager)
                getSystemService(Context.CONNECTIVITY_SERVICE);

        NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
        boolean isConnected = false;
        if (networkInfo != null && (isConnected = networkInfo.isConnected())) {
            // show "Connected" & type of network "WIFI or MOBILE"
            tvIsConnected.setText("Connected "+networkInfo.getTypeName());
            // change background color to red
            tvIsConnected.setBackgroundColor(0xFF7CCC26);
        } else {
            // show "Not Connected"
            tvIsConnected.setText("Not Connected");
            // change background color to green
            tvIsConnected.setBackgroundColor(0xFFFF0000);
        }

        return isConnected;
    }

   [HttpPost]  
        public async Task<HttpResponseMessage> insert()
        {
            string ret_msg = "";
               // take contents and do something
               var uploadPath = HostingEnvironment.MapPath("/") + @"/files/";
            Directory.CreateDirectory(uploadPath);
            var provider = new MultipartFormDataStreamProvider(uploadPath);
            await Request.Content.ReadAsMultipartAsync(provider);

            // Files
            foreach (MultipartFileData file in provider.FileData)
            {
                ret_msg += file.Headers.ContentDisposition.FileName;
                ret_msg += " / File : " + file.LocalFileName + " - ";
            }

            // Form data
            foreach (var key in provider.FormData.AllKeys)
            {
                foreach (var val in provider.FormData.GetValues(key))
                {
                    ret_msg += string.Format("{0}: {1}  - ", key, val);
                }
            }

            return Request.CreateResponse(HttpStatusCode.OK, ret_msg);
        }