using System;

using Newtonsoft.Json;

using Newtonsoft.Json.Serialization;

public class Program

{

    public static void Main()

    {

        var version1 = @"

        {

""id"" : 1,

""first_name"": ""Jon"",

""last_name"": ""Doe""

} 

        ";

        var version2 = @"

        {

    ""id"" : 1,

    ""firstName"": ""Jon"",

    ""lastName"": ""Doe""

    } 

        ";

        var jsonSerializerSettings = new JsonSerializerSettings();

        jsonSerializerSettings.MissingMemberHandling = MissingMemberHandling.Ignore;

        var p1 = JsonConvert.DeserializeObject<Person>(version1, jsonSerializerSettings);

        WritePerson(p1);

        var p2 = JsonConvert.DeserializeObject<Person>(version2, jsonSerializerSettings);

        WritePerson(p2);

    }

    private static void WritePerson(Person p) {

        Console.WriteLine($"{p.Id} - {p.FirstName} - {p.LastName}");

    }

}

​

public class Person

{

  public int Id {get; set;}

  [JsonProperty("firstName")]

  public string FirstName {get; set;}

  [JsonProperty("lastName")]

  public string LastName {get; set;}

  [JsonProperty("first_name")]

  public string __Ignore1 { set { FirstName = value; } }

  [JsonProperty("last_name")]

  public string __Ignore2 { set { LastName = value; } }

}

​