Reference remains null
-
27-10-2019 - |
문제
I think i ran into a bug, it seems that EF is not handling references well after deleting and reinserting an entity. I've managed to reproduce it with the code below (assume all asserts pass except the one i talk about in the comments):
var database = new TestEntities();
// select and delete the info record
var info = database.Info.First(i => i.ID == 1);
Assert.AreEqual(1, info.MemberID);
// when i uncomment the line below the last Assert fails
// Assert.IsNotNull(info.Member);
database.Info.Remove(info);
// add it again and persist it to the database
database.Info.Add(new Info {
ID = 1,
MemberID = 1
});
database.SaveChanges();
// should not be null ? EDIT: i guess i understand this becoming null
Assert.IsNull(info.Member);
// and even here its still null
info = database.Info.First(i => i.ID == 1);
Assert.IsNull(info.Member);
Can anyone tell me whats going on here?
EDIT:
My entities are generated using database first and im using the DbContext/POCO generator.
public partial class Member
{
public Member()
{
this.Info = new HashSet<Info>();
}
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<Info> Info { get; set; }
}
public partial class Info
{
public int ID { get; set; }
public int MemberID { get; set; }
public virtual Member Member { get; set; }
}
해결책
It turns out that it had nothing to do with deleting and reinserting, not really anyway. It was was so obvious ...
I was inserting using a POCO which is not eagerly loaded and does not have any lazy loading capabilities ...
The second time i queried for the same record i was expecting a proxy, but it seems that the POCO was cached by EF and that is what it returned meaning still no eager or lazy loading.
I can fix it by making sure EF doesn't retrieve the second query from cache, inserting using a proxy (var info = database.Info.Create()
) or including member in the query (database.Info.Include(i => i.Member).First(i => i == 1)
).
다른 팁
Given this
var info = database.Info.First(i => i.ID == 1);
Assert.AreEqual(1, info.MemberID);
Aren't you comparing info.ID to info.MemberID here? Isn't it possible that ID and MemberID actually are different?
Also, shouldn't you be using .SaveChanges() after
database.Info.Remove(info);
?
Also, info does not have .member available if none have been instantiated. Is there a correlating Member with MemberID equal to info.MemberId?