using System;

using System.Text.Json;

using System.Text.Json.Serialization;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

        var old = new OldNestClass(new TestClass1 { TestString = "T1" }, new TestClass2 { TestInt = 5 });

        var serialized = JsonSerializer.Serialize(old);

        Console.WriteLine("Old:" + serialized);

        var newVersion = JsonSerializer.Deserialize<NewNestClass>(serialized);

        var newVersionSerialied = JsonSerializer.Serialize(newVersion);

        Console.WriteLine(newVersion);

        Console.WriteLine("New:" + serialized);

    }

    public class OldNestClass 

    {

        public OldNestClass(TestClass1 testClass1, TestClass2 testClass2) {

            TestClass1 = testClass1;

            TestClass2 = testClass2;

        }

        public TestClass1 TestClass1 {get;  }

        public TestClass2 TestClass2 {get; }

    }

    public class NewNestClass 

    {

        public NewNestClass(TestClass1 testClass1, TestClass2 testClass2, NewTestClass newTestClass) {

            TestClass1 = testClass1;

            TestClass2 = testClass2;

            NewTestClass = newTestClass;

        }

        public TestClass1 TestClass1 {get;  }

        public TestClass2 TestClass2 {get; }

        public NewTestClass NewTestClass {get; }

    }

    public class TestClass1 

    {

        public string TestString {get; set; }

    }

    public class TestClass2 

    {

        public int TestInt {get; set; }

    }

    public class NewTestClass 

    {

        public string TestString {get; set; }

    }

}