I have a class 'Hand' that consists of two playing cards as below:

public class Card
{
    public char r, s;

    public Card(char rank, char suit)
    {
        r = rank;
        s = suit;
    }
}

public class Hand
{
    public Card c1, c2;

    public Hand(Card one, Card two)
    {
        c1 = one;
        c2 = two;
    }
}

In a 52 card deck we can't have two identical cards. How should I deal with an error where I accidentally instance a class with two identical cards, e.g (Ah, Ah)?

Thanks, Ash