using System;

using System.Linq;

using System.Collections.Generic;

using Newtonsoft.Json;

public class Program

{

    public static void Main()

    {

        var serializationSettings = new JsonSerializerSettings

        {

            MetadataPropertyHandling = MetadataPropertyHandling.Ignore

        };

        JsonConvert.DefaultSettings = () => serializationSettings;

        User.NoIssue();

        User.MissingKey();

        User.ShowIssue();

    }

}

​

​

public class User

    {

        public string name { get; set; }

        public int age { get; set; }

​

        public static void ShowIssue()

        {

            var dic = new Dictionary<string, User> {

                {"$id", new User() { name = "Hello", age = 26 } },

                {"value", new User() { name = "Hello2", age = 28 } },

            };

​

            var str = JsonConvert.SerializeObject(dic);

            Console.WriteLine(str);

​

            var dic2 = JsonConvert.DeserializeObject<Dictionary<string, User>>(str);

            Console.WriteLine(string.Join(", ", dic2.Keys.ToArray()));

        }

​

        public static void NoIssue()

        {

            var dic = new Dictionary<string, User> {

                {"$value", new User() { name = "Hello", age = 26 } },

                {"value", new User() { name = "Hello2", age = 28 } },

            };

​

            var str = JsonConvert.SerializeObject(dic);

            Console.WriteLine(str);

​

            var dic2 = JsonConvert.DeserializeObject<Dictionary<string, User>>(str);

            Console.WriteLine(string.Join(", ", dic2.Keys.ToArray()));

        }

​

        public static void MissingKey()

        {

            var dic = new Dictionary<string, int> {

                {"$id", 26 },

                {"value",  28 },

            };

​

            var str = JsonConvert.SerializeObject(dic);

            Console.WriteLine(str);

​

            var dic2 = JsonConvert.DeserializeObject<Dictionary<string, int>>(str);

            Console.WriteLine(string.Join(", ", dic2.Keys.ToArray()));

        }

    }