Linq select为两个嵌套对象之一返回null

Question

I have a Linq select statement that is supposed to return objects that have 2 nested objects. The problem is, one of the nested objects is returning null while the other is working as intended.

Here is the object being queried:

public class CharInvCard
{
    public int ID { get; set; }
    public Character Character { get; set; }
    public Card Card { get; set; }
    public bool inDeck { get; set; }
    public bool inHand { get; set; }
    public bool inDiscard { get; set; }
}

Here is my Linq query:

IQueryable<CharInvCard> CardsInHand = from x in db.CharInvCards
                               where x.Character.ID == character.ID && x.inHand == true
                               select x;

After getting the results of this query I do a foreach loop that starts like this:

foreach (CharInvCard deckCardRec in CardsInHand)

While debugging, if I inspect the contents of deckCardRec I see that it has all its properties for ID, inHand, inDeck, inDiscard and even a nested Character object (and its properties) but Card is always null.

I've checked and double checked that the Card_Id column in my database is populated with the proper ID corresponding to the Card table.

What is causing the Card nested object is returned as null while the Character nested object to be returned properly?

Answer 1

You are referencing Character in your linq query, so it is included. You are not referencing Card though. Try eager loading Cards as below:

IQueryable<CharInvCard> CardsInHand = from x in db.CharInvCards.Include("Cards")
                               where x.Character.ID == character.ID && x.inHand == true
                               select x;

I have assumed your navigational property is named "Cards" above.