Model model=JsonConvert.DeserializeObject<Model>(val);

string jsonString = JsonConvert.SerializeObject(obj);

var jsonSetting = new JsonSerializerSettings {NullValueHandling = NullValueHandling.Ignore};

var json = JsonConvert.SerializeObject（data， Formatting.Indented， jsonSetting）;

"MemberQuery": {
      "PhoneNumber": "13222222222",
      "Name": "test",
      "MF": "女",
      "BirthDate": "01/01/2017",
      "MaritalStatus": null,
      "Country": null
}

"MemberQuery": {
    "PhoneNumber": "13222222222",
    "Name": "test",
    "MF": "女",
    "BirthDate": "01/01/2017"
}