Bitrix24 Rest API post request using ASP.NET

Question

Bitrix24 CRM have webhook functional to add leads (clients) to CRM. All documentation is written on php, but I want to use ASP.NET. Here's how they do it on php:

$queryUrl  = 'https://restapi.bitrix24.ru/rest/1/31uhq2q855fk1foj/crm.lead.add.json';
$queryData = http_build_query(array(
    'fields' => array(
        "TITLE" => "NEW LEAD"
    ),
    'params' => array(
        "REGISTER_SONET_EVENT" => "Y"
    )
));

$curl = curl_init();
curl_setopt_array($curl, array(
    CURLOPT_SSL_VERIFYPEER => 0,
    CURLOPT_POST => 1,
    CURLOPT_HEADER => 0,
    CURLOPT_RETURNTRANSFER => 1,
    CURLOPT_URL => $queryUrl,
    CURLOPT_POSTFIELDS => $queryData
));

$result = curl_exec($curl);
curl_close($curl);

$result = json_decode($result, 1);

I'm trying to do the same thing using ASP.NET, but get error 400 as a response. I almost sure that the problem is in the request parameters, line const string data = @"[{""fields"":{""title"":""Test""}}]";. I've tried tons of combinations, but nothing worked.

const string url = @ "https://companyname.bitrix24.ru/rest/14/31uhq2q855fk1foj/crm.lead.add.json";
const string data = @"[{""fields"":{""title"":""Test""}}]";

HttpClient client = new HttpClient();
client.BaseAddress = new Uri(url);
byte[] cred = Encoding.UTF8.GetBytes("email:password");
client.DefaultRequestHeaders.Authorization = new System.Net.Http.Headers.AuthenticationHeaderValue("Basic", Convert.ToBase64String(cred));
client.DefaultRequestHeaders.Accept.Add(new System.Net.Http.Headers.MediaTypeWithQualityHeaderValue("application/json"));

HttpContent content = new StringContent(data, Encoding.UTF8, "application/json");
HttpResponseMessage messge = client.PostAsync(url, content).Result;
string description;
if (messge.IsSuccessStatusCode) {
    string result = messge.Content.ReadAsStringAsync().Result;
    description = result;
}

Answer 1

Bitrix24 support are very "happy" with php and does not know about other languages :( After some investigations I found way with anonymous objects and json.net. Your sample should looks like:

var data = new {
  fields = new {
    TITLE = "NEW LEAD"
  },
  @params = new {
    REGISTER_SONET_EVENT = "Y"
  }
};
var contentText = JsonConvert.SerializeObject(data);

var content = new StringContent(contentText, Encoding.UTF8, "application/json");
// and so on with HttpClient

Update Dec 13:

Sometimes you can't (or don't want) put field names directly into anonymous object. So, dictionary may be used:

var data = new
{
    ID = someId,
    FIELDS = new Dictionary<string, object>()
    {
        [options.SomeFieldName] = fieldValue,
    },
};