Design Patterns - Factory Method

--- program.cs  ---
namespace GoFFactoryMethod
{
    internal class Program
    {
        static void Main(string[] args)
        {
            ICreditCardFactory factory = new CreditCardFactory();

            Correntista correntista = new Correntista()
            {
                ID = 123,
                DataNascita = new DateTime(1970, 4, 22),
                StatoLavorativo = StatoLavorativo.Imprenditore,
                RedditoAnnuo = 157000,
                Saldo = 42000
            };

            correntista.CreditCard = factory.CreateCreditCard(correntista);

            if (correntista.CreditCard is null)
            {
                Console.WriteLine("Nessuna carta di credito disponibile");
            }
            else
            {
                Console.WriteLine($"Carta: {correntista.CreditCard.Nome} - Limite: {correntista.CreditCard.Limite:N2}");
            }
            Console.ReadKey();
        }
    }
}
-----------------------------------------------------------------------

--- correntista.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GoFFactoryMethod
{
    public enum StatoLavorativo
    {
        Studente,
        Disoccupato,
        Lavoratore,
        Imprenditore,
        Pensionato
    }

    public interface ICorrentista
    {
        public StatoLavorativo StatoLavorativo { get; }
        public int Anni { get; }
    }

    public class Correntista : ICorrentista
    {
        public int ID { get; set; }

    /*
     * private int id = 0;
     *
     * public int ID() {return id;}
     */


        public DateTime DataNascita { get; set; }
        public StatoLavorativo StatoLavorativo { get; set; }
        public decimal RedditoAnnuo { get; set; }

        public ICreditCard? CreditCard { get; set; } = null;

        public decimal Saldo { get; set; }
        public int Anni
        {
            get
            {
                long ticks = DateTime.Now.Subtract(DataNascita).Ticks;
                return new DateTime(ticks).Year;
            }
        }
    }
}
-----------------------------------------------------------------------------

--- ICreditCard.cs ---
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GoFFactoryMethod
{
    public interface ICreditCard
    {
        string Nome { get; }
        decimal Limite { get; }
        void Paga();
    }

    internal abstract class CreditCard : ICreditCard
    {
        protected string nome = String.Empty;

        protected decimal limite;

        public string Nome
        {
            get => nome;
        }

        public decimal Limite
        {
            get => limite;
        }
        public virtual void Paga() { }
    }

    internal class PrimaCreditCard : CreditCard
    {
        public PrimaCreditCard(decimal limite)
        {
            nome = "Carta Prima";
            this.limite = limite;
        }
    }

    internal class ClassicCreditCard : CreditCard
    {
        public ClassicCreditCard(decimal limite)
        {
            nome = "Carta Classic";
            this.limite = limite;
        }
    }
}
------------------------------------------------------------------------------

--- CreditCardFactory ---
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GoFFactoryMethod
{
    public interface ICreditCardFactory
    {
        ICreditCard? CreateCreditCard(ICorrentista correntista);
    }


    public abstract class AbstractCreditCardFactory : ICreditCardFactory
    {
        public abstract ICreditCard? CreateCreditCard(ICorrentista correntista);
    }

    public class CreditCardFactory : AbstractCreditCardFactory
    {
        public override ICreditCard? CreateCreditCard(ICorrentista correntista)
        {
            ICreditCard? card = null;
            switch (correntista.StatoLavorativo)
            {
                case StatoLavorativo.Disoccupato:
                    break;

                case StatoLavorativo.Studente:
                    card = new PrimaCreditCard(500);
                    break;

                case StatoLavorativo.Lavoratore:
                    card = new ClassicCreditCard(1000);
                    break;

                case StatoLavorativo.Imprenditore:
                    card = new ClassicCreditCard(2000);
                    break;
            }

            return card;
        }
    }
}