System.Linq和IEnumerable组帮助

我只是用LINQ和IEnumerable把脚弄湿了,我需要帮助确定我的对象是否包含纸牌游戏的匹配项。我想如果我先弄清楚第一个,我需要做的另一个匹配检查就会到位。

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?
}