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"
}