using System;

using System.Linq;

using Newtonsoft.Json.Linq;

​

public static class Program

{

    public static void Main(string[] args)

    {

        var json = JObject.Parse(@"{""DanaerysTargaryen"":{""Dragons"":{""Dragon1"":{""Name"": ""Drogon""}},""Hair"": {""Color"": ""White""}}}");

        var toMerge = @"{""DanaerysTargaryen"":{""Dragons"":{""Dragon1"":{""Color"":""Black""}}}}";

        var jsonToMerge = JObject.Parse(toMerge);

        json.Merge(jsonToMerge);

        Console.WriteLine(json.ToString());

    }

}