using System;

using System.Text.Json;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var json = "[{\"id\":1,\"timeFrom\":\"7:00:00\",\"timeTo\":\"12:00:00\",\"description\":null,\"isAllDay\":false},{\"id\":2,\"timeFrom\":\"12:00:00\",\"timeTo\":\"16:00:00\",\"description\":null,\"isAllDay\":false},{\"id\":3,\"timeFrom\":\"16:00:00\",\"timeTo\":\"21:00:00\",\"description\":null,\"isAllDay\":false},{\"id\":4,\"timeFrom\":\"7:00:00\",\"timeTo\":\"21:00:00\",\"description\":\"Cały dzień\",\"isAllDay\":true},{\"id\":5,\"timeFrom\":\"7:00:00\",\"timeTo\":\"21:00:00\",\"description\":\"Sobota\",\"isAllDay\":true},{\"id\":6,\"timeFrom\":\"7:00:00\",\"timeTo\":\"21:00:00\",\"description\":\"Nie ustaliłem/am\",\"isAllDay\":true}]";

        try{

            var js = JsonSerializer.Deserialize<List<ClientAvailabilitySlotExt>>(json);

            foreach(var i in js)

            {

                Console.WriteLine(i.id);

            }

        }

        catch(Exception ex){

            Console.WriteLine(ex.Message);  

        }

        Console.WriteLine("Hello World2");

    }

​

}

public sealed class ClientAvailabilitySlotExt

{

    public int id { get; set; }

    public TimeSpan? timeFrom { get; set; }

    public string? timeTo { get; set; }

    public string? Description { get; set; }

    public bool IsAllDay { get; set; }

}