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.Text.Json;

using System.Text.Json.Serialization;

​

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

​

//https://stackoverflow.com/questions/72774698/system-text-json-serialization-doesnt-work-for-abstract-members

​

#nullable enable

​

public interface IAmount {

    decimal Value { get; }

}

​

[Newtonsoft.Json.JsonConverter(typeof(NewtonsoftJsonConverter))]

[System.Text.Json.Serialization.JsonConverter(typeof(SystemTextJsonConverter))]

public class Amount : IAmount {

    public Amount(decimal value) {

        Value = value;

    }

​

    public decimal Value { get; }

}

​

public class NewtonsoftJsonConverter : Newtonsoft.Json.JsonConverter {

    public override bool CanConvert(Type objectType) => objectType.IsAssignableTo(typeof(IAmount));

​

    public override object? ReadJson(Newtonsoft.Json.JsonReader reader, Type objectType, object? existingValue, Newtonsoft.Json.JsonSerializer serializer) {

        throw new NotImplementedException();

    }

​

    public override void WriteJson(Newtonsoft.Json.JsonWriter writer, object? value, Newtonsoft.Json.JsonSerializer serializer) {

        writer.WriteRawValue(((IAmount?)value)?.Value.ToString());

    }

}

​

public class SystemTextJsonConverter : System.Text.Json.Serialization.JsonConverter<object> {

    public override bool CanConvert(Type typeToConvert) => typeToConvert.IsAssignableTo(typeof(IAmount));

​

    public override object Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options) {

        throw new NotImplementedException();

    }

​

    public override void Write(System.Text.Json.Utf8JsonWriter writer, object value, System.Text.Json.JsonSerializerOptions options) {

        writer.WriteRawValue(((IAmount)value).Value.ToString());

    }

}

​

    public class ConcreteInterfaceSerializer : JsonConverterFactory

    {

        public override bool CanConvert(Type typeToConvert) => typeToConvert.IsInterface;

        class ConcreteInterfaceSerializerOfType<TInterface> : JsonConverter<TInterface> 

        {

            static ConcreteInterfaceSerializerOfType()

            {

                if (!typeof(TInterface).IsAbstract && !typeof(TInterface).IsInterface)

                    throw new NotImplementedException(string.Format("Concrete class {0} is not supported", typeof(TInterface)));

            }   

            public override TInterface? Read(ref System.Text.Json.Utf8JsonReader reader, Type typeToConvert, System.Text.Json.JsonSerializerOptions options) =>

                throw new NotImplementedException();

​

            public override void Write(System.Text.Json.Utf8JsonWriter writer, TInterface value, System.Text.Json.JsonSerializerOptions options) =>

                JsonSerializer.Serialize<object>(writer, value!, options);

        }

        public override JsonConverter CreateConverter(Type type, JsonSerializerOptions options) => 

            (JsonConverter)Activator.CreateInstance(

                typeof(ConcreteInterfaceSerializerOfType<>).MakeGenericType(new Type[] { type }),

                BindingFlags.Instance | BindingFlags.Public,

                binder: null,

                args: Array.Empty<object>(),

                culture: null).ThrowOnNull();

    }

​

    public static class ObjectExtensions

    {

        public static T ThrowOnNull<T>(this T? value) where T : class => value ?? throw new ArgumentNullException();

    }

​

    class TestClass

    {

        public static void Test()

        {

            var foo = new Amount(10);

​

            var newtonJson = Newtonsoft.Json.JsonConvert.SerializeObject(foo); // 10

            var options = new JsonSerializerOptions

            {

                Converters = { new ConcreteInterfaceSerializer() },

            };

            var systemJson = System.Text.Json.JsonSerializer.Serialize<IAmount>(foo, options);

            Console.WriteLine("Newtonsoft JSON:\n {0}", newtonJson);

            Console.WriteLine("System.Text.Json JSON:\n {0}", systemJson);

            Assert.AreEqual(newtonJson, systemJson);

        }   

    }

​

    public class Program

    {

        public static void Main()

        {

            Console.WriteLine("Environment version: {0} ({1}), {2}", System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription , Environment.Version, Environment.OSVersion);

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

            Console.WriteLine();

​

            try

            {

                TestClass.Test();

            }

            catch (Exception ex)

            {

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

                Console.WriteLine(ex);

                throw;

            }

        }

    }

​