System.Linq and IEnumerable Group Help

I'm just getting my feet wet with Linq and IEnumerable, and I'm needing help in trying to determine if my objects contain matches for a card game. I think if I get the first one 开发者_StackOverflow社区figured out, the other match checking I need to do will fall in place.

public class Card
{
    pubic int Value { get; set; }
    public Card(int value)
    {
        this.Value = value;
    }
}

public bool IsCompletedSet(List<Card> cards)
{
    var cardValueGroups = cards.GroupBy(card => card.Value);
    //How do I determine that there are now exactly two groups of cards
    //and that each group contains exactly 3 cards each?
}

To get the number of groups:

cardValueGroups.Count()

To make sure they all have exactly three cards:

cardValueGroups.All(g => g.Count() == 3)