C#/LINQ 查询类

Question

我正在使用 Sam Jenkin's Deck of Cards class .我正在尝试查询套装中的某些卡片。我收到错误:

Cannot implicitly convert type 'System.Collections.Generic.IEnumerable' to 'System.Collections.Generic.IEnumerable'. An explicit conversion exists (are you missing a cast?)

我试过四处移动东西，但我不明白这个错误。有人可以帮忙吗？我的代码是:

var deck = new Deck();

IEnumerable<Deck> deckQuery =
            from myCard in deck.Cards
            where myCard.Suit == Suit.Club
            select myCard.CardNumber;

我的 Card 类是:

public class Card : ICard
{
    public Suit Suit { get; set; }
    public CardNumber CardNumber { get; set; }
}

我的枚举数是:

public enum Suit
{
    Club = 1,
    Diamond = 2,
    Heart = 3,
    Spades = 4,
}

public enum CardNumber
{
    Ace = 1,
    Two = 2,
    Three = 3,
    Four = 4,
    Five = 5,
    Six = 6,
    Seven = 7,
    Eight = 8,
    Nine = 9,
    Ten = 10,
    Jack = 11,
    Queen = 12,
    King = 13,
}

Answer 1

您正在选择一个 CardNumber，但试图将它放入一副牌中:

// This won't work:
// IEnumerable<Deck> deckQuery =
IEnumerable<CardNumber> deckQuery = 
        from myCard in deck.Cards
        where myCard.Suit == Suit.Club
        select myCard.CardNumber;

另一种选择是选择卡片本身:

IEnumerable<Card> deckQuery = 
        from myCard in deck.Cards
        where myCard.Suit == Suit.Club
        select myCard;