Seriyi Günceller

var options = new RestClientOptions("https://apitest.nilvera.com")
{
  MaxTimeout = -1,
};
var client = new RestClient(options);
var request = new RestRequest("/ebill/Series", Method.Put);
request.AddHeader("Authorization", "Bearer <API KEY>");
request.AddHeader("Content-Type", "application/json");
var body = @"{
"ID": 0,
"IsDefault": true,
"IsActive": true}";
request.AddStringBody(body, DataFormat.Json);
RestResponse response = await client.ExecuteAsync(request);
Console.WriteLine(response.Content);