using System;

​

class DefuncionDetalle

{

    public string? f { get; set; }

    public string? h { get; set; }

​

    public DefuncionDetalle(string? fecha, string? hora)

    {

        f = fecha;

        h = hora;

    }

}

​

class Program

{

    static void Main()

    {

        var pruebas = new[]

        {

            new DefuncionDetalle(null, null),

            new DefuncionDetalle("2025-03-13", null),

            new DefuncionDetalle(null, "14:30"),

            new DefuncionDetalle("2025-03-13", "14:30")

        };

​

        foreach (var prueba in pruebas)

        {

            string json = System.Text.Json.JsonSerializer.Serialize(new { f = prueba.f ?? string.Empty, h = prueba.h ?? string.Empty });

            Console.WriteLine(json);

        }

    }

}