using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Runtime.Serialization.Formatters;

using System.IO;

using System.Data;

using System.ComponentModel.DataAnnotations;

using System.Globalization;

using System.Reflection;

using System.Collections.ObjectModel;

using System.Runtime.Serialization;

​

using Newtonsoft.Json;

using Newtonsoft.Json.Linq;

using Newtonsoft.Json.Converters;

using Newtonsoft.Json.Serialization;    

​

using NUnit.Framework; // Throws NUnit.Framework.AssertionException

​

//https://stackoverflow.com/questions/65347359/serialization-problem-in-a-custom-collection-with-a-private-list

​

    class ListCollection : List<int>

    {

    }

​

    [Serializable]

    [JsonConverter(typeof(PrivateListCollectionConverter))]

    class PrivateListCollection: ISerializable

    {

        private List<int> list = new List<int>();

​

        public void Add(int value)

        {

            list.Add(value);

        }

​

        public void GetObjectData(SerializationInfo info, StreamingContext context)

        {

            info.AddValue("items", list);

        }

    }

​

    class PrivateListCollectionConverter : JsonConverter<PrivateListCollection>

    {

        const string itemsName = "items";

        public override PrivateListCollection ReadJson(JsonReader reader, Type objectType, PrivateListCollection existingValue, bool hasExistingValue, JsonSerializer serializer)

        {

            var list = serializer.Deserialize<List<int>>(reader);

            if (list == null)

                return null;

            existingValue = existingValue ?? new PrivateListCollection();

            foreach (var item in list)

                existingValue.Add(item);

            return existingValue;

        }

​

        public override void WriteJson(JsonWriter writer, PrivateListCollection value, JsonSerializer serializer)

        {

            // There doesn't seem to be any way to extract the items from the PrivateListCollection other than to call GetObjectData(), so let's do that.

            // Adding PrivateListCollectionConverter as a nested type inside PrivateListCollection would be another option to make the items accessible.

            ISerializable serializable = value;

            var info = new SerializationInfo(value.GetType(), new FormatterConverter());

            serializable.GetObjectData(info, serializer.Context);

            var list = info.GetValue(itemsName, typeof(IEnumerable<int>));

            serializer.Serialize(writer, list);

        }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var list1 = new ListCollection { 1, 2, 3 };

            var list2 = new PrivateListCollection();

            foreach (var item in list1)

                list2.Add(item);

            var settings = new JsonSerializerSettings

            {

                Converters = { new PrivateListCollectionConverter() },

            };

            var json1 = JsonConvert.SerializeObject(list1, settings);

            var json2 = JsonConvert.SerializeObject(list2, settings);

            Console.WriteLine(json2);

            Assert.AreEqual(json1, json2);

            var list22 = JsonConvert.DeserializeObject<PrivateListCollection>(json1, settings);

            var json22 = JsonConvert.SerializeObject(list22, settings);

            Assert.AreEqual(json2, json22);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1})", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , GetNetCoreVersion());

            Console.WriteLine("{0} version: {1}", typeof(JsonSerializer).Assembly.GetName().Name,  typeof(JsonSerializer).Assembly.FullName);

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

                Console.WriteLine("Failed with unhandled exception: ");

                Console.WriteLine(ex);

                throw;

            }

        }

        public static string GetNetCoreVersion()

        {

            //https://techblog.dorogin.com/how-to-detect-net-core-version-in-runtime-ecd65ad695be

            //

            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;

            var assemblyPath = assembly.Location.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);

            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");

            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)

                return assemblyPath[netCoreAppIndex + 1];

            return null;

        }

    }

​