using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

using System.Text;

​

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

​

[JsonDerivedType(typeof(ClassB), nameof(ClassB))]

[JsonDerivedType(typeof(ClassA), nameof(ClassA))]

[JsonPolymorphic(TypeDiscriminatorPropertyName = "TypeDiscriminator")]

public abstract class ClassC

{

    public string PropertyC { get; set; }

}

​

[JsonDerivedType(typeof(ClassB), nameof(ClassB))]

[JsonPolymorphic(TypeDiscriminatorPropertyName = "TypeDiscriminator")]

public class ClassB : ClassC

{

    public string PropertyB { get; set; }

}

​

[JsonDerivedType(typeof(ClassA), nameof(ClassA))]

[JsonPolymorphic(TypeDiscriminatorPropertyName = "TypeDiscriminator")]

public class ClassA : ClassB

{

    public string PropertyA { get; set; }

}

​

​

    class TestClass

    {

        public static void Test()

        {

            var options = new JsonSerializerOptions

            {

                WriteIndented = true

            };

​

            ClassA classA = new ClassA { PropertyA = "ValueA", PropertyB = "ValueB", PropertyC = "ValueC" };

​

            string json = JsonSerializer.Serialize<ClassC>(classA, options);

            Console.WriteLine(json);

            ClassC deserialized = JsonSerializer.Deserialize<ClassC>(json, options)!;

​

            Console.WriteLine(deserialized is ClassA); // Should output 'True'

        }   

    }

​

    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;

            }

        }

    }

​