using System;

using System.Collections.Generic;

using System.Collections.ObjectModel;

using System.Linq;

using System.Text.Json;

using System.Text.Json.Serialization;

public class Program

{

    public static void Main()

    {

        var options = new JsonSerializerOptions()

        {

            WriteIndented = true

        };

​

        var items = new[] { "A", "B", "C" };

        var instance = new SomeClass(items);

​

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

        Console.WriteLine(json);

        Console.WriteLine();

​

        var copy = JsonSerializer.Deserialize<SomeClass>(json, options);

    }

}

​

public sealed class SomeClass

{

    [JsonConstructor()]

    public SomeClass(IEnumerable<string> myItems)

    {

        InternalMyItems = new Collection<string>(myItems.ToArray());

        MyItems = new ReadOnlyCollection<string>(InternalMyItems);

    }

    public IReadOnlyCollection<string> MyItems { get; }

    private Collection<string> InternalMyItems { get; }

}

​