Pincode en klassen

class Program
{
	static void Main(string[] args)
	{
		var atm = new AtmMachine();
		var companyCard = new Card("Company Account", "1234");

		try
		{
			atm.InsertCard(companyCard);
			Console.WriteLine("Card '{0}' has been inserted, please enter PIN", atm.CurrentCardAccountName);

			while (true)
			{
				var input = Console.ReadLine(); //validate input etc...

				var validPin = atm.EnterPin(input);

				if (validPin)
				{
					Console.WriteLine("Pin correct, start withdraw sequence");
					//rest of the withdraw code here
					break;
				}

				if (atm.MaxAttemptsReached)
				{
					Console.WriteLine("Max attempts reached, card blocked. Contact bank.");
					atm.EjectCurrentCard();
					break;
				}

				Console.WriteLine("PIN invalid, please try again");
			}

			atm.EjectCurrentCard();
		}
		catch (CardBlockedException ex)
		{
			Console.WriteLine(ex.Message);
			atm.EjectCurrentCard();
		}

		Console.ReadLine();
	}
}


public class AtmMachine
{
	private const int MaxAttempts = 3;

	private Card _currentCard;
	private int _attempts;

	public bool EnterPin(string pinCode)
	{
		if (pinCode == _currentCard.Pin)
			return true;

		_attempts++;

		if (MaxAttemptsReached)
			BlockCurrentCard();

		return false;
	}

	public bool MaxAttemptsReached
	{
		get { return _attempts >= MaxAttempts; }
	}

	public string CurrentCardAccountName
	{
		get { return _currentCard.Account; }
	}

	public void InsertCard(Card card)
	{
		if (card.IsBlocked)
			throw new CardBlockedException();

		_currentCard = card;
		_attempts = 0;
	}

	public void EjectCurrentCard()
	{
		_currentCard = null;
	}

	public void BlockCurrentCard()
	{
		_currentCard.Block();
	}
}

public class CardBlockedException : Exception
{
	public CardBlockedException()
		: this("The card has been blocked")
	{
	}

	public CardBlockedException(string message)
		: base(message)
	{

	}
}

public class Card
{
	private readonly string _account;
	private readonly string _pin;
	private bool _isBlocked;

	public Card(string account, string pin)
	{
		_account = account;
		_pin = pin;
	}

	public bool IsBlocked
	{
		get { return _isBlocked; }
	}

	public string Pin
	{
		get { return _pin; }
	}

	public string Account
	{
		get { return _account; }
	}

	public void Block()
	{
		_isBlocked = true;
	}
}