"filters": {
    "phone": "+123456789",
    "date_from": null,
    "date_to": null,
    "status_id": 10,
    "sender_phone": "",
    "receiver_phone": "",
    "sender_name": "",
    "receiver_name": "",
    "sender_city": "",
    "receiver_city": ""
  }

  "filters": {
    "phone": "+123456789",
    "status_id": 10
  }

            var str = JsonConvert.SerializeObject(
                this, 
                Formatting.Indented,
                new JsonSerializerSettings
                {
                    DefaultValueHandling = DefaultValueHandling.Ignore,
                    NullValueHandling = NullValueHandling.Ignore
                });
        }