using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Data;

​

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

​

//https://stackoverflow.com/questions/77840303/can-i-shorten-types-names-while-serializing

​

[JsonPolymorphic(TypeDiscriminatorPropertyName = "__type")] // Add this here

[JsonDerivedType(typeof(Person), typeDiscriminator: "P")]

[JsonDerivedType(typeof(Adult), typeDiscriminator: "A")]

public class Person

{

    public string Name { get; set; }

}

​

[JsonPolymorphic(TypeDiscriminatorPropertyName = "__type")] // And also here

[JsonDerivedType(typeof(Adult), typeDiscriminator: "A")]

public class Adult : Person;

​

​

#nullable enable

​

    class TestClass

    {

        public static void Test()

        {

            var people = new Person[] { new Person { Name = "AbcPerson" }, new Adult { Name = "foo" } };

            var json = JsonSerializer.Serialize(people);

            var people2 = JsonSerializer.Deserialize<Person []>(json);

​

            Console.WriteLine(json);

            Assert.That(json.Contains("\"__type\""));

            Assert.That(!json.Contains("\"$type\""));

            Assert.That(people.Select(p => p.GetType()).SequenceEqual(people2!.Select(p => p.GetType())));

        }   

    }

​

    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;

            }

        }

    }

​