using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Diagnostics;

using System.IO;

using System.Threading;

using System.Collections.ObjectModel;

using System.Globalization;

using System.Net;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;

​

​

// https://stackoverflow.com/questions/44797731/adding-jarray-to-a-existing-property

​

    internal class Product

    {

        public int ID { get; set; }

        public string Name { get; set; }

    }

​

​

    class TestClass

    {

        public static void Test()

        {

            var products= new List<Product>()

            {

                new Product() {ID=1,Name="AA" },

                new Product() {ID=2,Name="BB" }

            };

​

            var JSONstr = GetJson();

            var JSON = JObject.Parse(JSONstr);

​

            JSON["Products"] = JToken.FromObject(products);

​

            JSON["TimeStamp"] = JToken.FromObject(DateTime.UtcNow);

            Console.WriteLine(JSON);

        }

        static string GetJson()

        {

            var json = @"{

  ""ID"":123,

  ""Products"":null,

  ""Title"":""Products""

}";

            return json;

        }

    }

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: " + Environment.Version);

            Console.WriteLine("Json.NET version: " + typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine("");

            TestClass.Test();

        }

    }

​