C# Json.Net serialize Dictionary<string, object>. You can run it on: http://rextester.com/JOT81793

csharp-json-serialize.cs

//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            Dictionary<string, object> points = new Dictionary<string, object>
            {
                { "James", 9001 },
                { "Jo", "This is a string" },
                { "Jess", null }
            };
            points.Add("array", new object[]{"a", "b", 3});

            string json = JsonConvert.SerializeObject(points, Formatting.Indented);

            Console.WriteLine(json);
            // {
            //   "James": 9001,
            //   "Jo": 3474,
            //   "Jess": 11926
            //   "array": [
            //     "a",
            //     "b",
            //     3
            //   ]
            // }
        }
    }
}