Question

I’m trying to deep-load a EF object and keep it in cache for a certain period. In my case, I have an object (say User) and then an internal list of Books set as a virtual collection

public virtual ICollection<Books> ListOfBooks { get; set; }

Where there’s a foreign key relation between Books and User (and it all works fine)

I’m trying to deep-load this in a static central class

public static List<User> LoadAllBooksAndUsers() {

  using (MyDB dc = new MyDB())
  {

      dc.Users.Include("ListOfBooks");
      List<User> a = dc.Users.Where(l => l.Status == 1).ToList();

      return a;             
   }
}

In my calling code, I have something like this:

var evx = DB.LoadAllBooksAndUsers();
var q = evx.Single(m=>m.name==name);

Examining evx in the debugger or q.ListOfBooks shows that the listOfBooks has an objects disposed exception and it is null.

And this is random – it seems to work once in a while and I don’t know under what condition.

I’m clueless as to what’s happening – my understanding is that using .Include() and then enumerating it will load all dependent foreign key objects, so why isn’t the method deep-loading all books into the user? What am I missing?

(I’d like to deep-load this object and cache it for a while as the data in it is used frequently)

Answer 1

You are using the Include wrong. You need to use it together with the query building not in itself:

List<User> a = dc.Users.Include("ListOfBooks")
                       .Where(l => l.Status == 1)                           
                       .ToList();

You can find more info in this article about eager loading.