using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Data;

using System.Reflection;

​

using System.Text.Json;

using System.Text.Json.Serialization;

using System.Text.Json.Serialization.Metadata;

using System.Text.Json.Nodes;

​

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

​

public class MyBaseClass;

​

public abstract class ValueObject;

​

public class MyValueObject : ValueObject;

​

//https://stackoverflow.com/questions/77809445/custom-typeinforesolver-to-manage-polimorphic-deserialization-in-system-text-jso

​

#nullable enable

​

    public static class JsonExtensions

    {

        public static void AddNativePolymorphicTypInfo(JsonTypeInfo jsonTypeInfo)

        {

            Type baseValueObjectType = typeof(ValueObject);

            if (jsonTypeInfo.Type == baseValueObjectType) {

                jsonTypeInfo.PolymorphismOptions = new JsonPolymorphismOptions {

                    TypeDiscriminatorPropertyName = "$mytype",

                    IgnoreUnrecognizedTypeDiscriminators = true,

                    UnknownDerivedTypeHandling = JsonUnknownDerivedTypeHandling.FailSerialization,

                };

                var types = Assembly

                    .GetExecutingAssembly()

                    .GetTypes()

                    .Where(t => t.IsSubclassOf(typeof(ValueObject))); // Fixed MyBaseClass => ValueObject

                foreach (var t in types.Select(t => new JsonDerivedType(t, t.Name.ToLowerInvariant()))) // Fixed ToLower() => ToLowerInvariant

                    jsonTypeInfo.PolymorphismOptions.DerivedTypes.Add(t);

            }

        }

    }

​

    public class RootObject

    {

        public ValueObject? ValueObject { get; set; }

    }

​

    class TestClass

    {

        public static void Test()

        {

            var rootObject = new RootObject { ValueObject = new MyValueObject() };

            var options = new JsonSerializerOptions

            {

                TypeInfoResolver = new DefaultJsonTypeInfoResolver() // Or use some source-generated context if you prefer

                    .WithAddedModifier(JsonExtensions.AddNativePolymorphicTypInfo),

                // Add other options as required, e.g.

                PropertyNamingPolicy = JsonNamingPolicy.CamelCase,

            };

            var json = JsonSerializer.Serialize(rootObject, options);

            Console.WriteLine(json);

            Assert.That("""{"valueObject":{"$mytype":"myvalueobject"}}""" == json);

        }   

    }

​

    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;

            }

        }

    }

​