Question

I have an User class that have the following fields:

public int Id { get; set; }
public ICollection<Event> AdminEvents { get; set; }
public ICollection<Event> SubscribedEvents { get; set; }

And my Event class looks like:

public int Id { get; set; }
public ICollection<User> Subscribed { get; set; }
public User Admin { get; set; }
public int AdminId { get; set; }

OnModelCreating in my Context:

modelBuilder.Entity<User>().HasMany(u => u.SubscribedEvents).WithMany(u => u.Subscribed);
modelBuilder.Entity<User>().HasMany(u => u.AdminEvents).WithRequired(u => u.Admin).WillCascadeOnDelete(false);

---

• The point here is that User can create an Event (Event.Admin && Admin.Id) and can be subscribed to others events (User.SubscribedEvents && Event.Subscribed)

• When i try to access User.SubcribedEvents.ToList() it throws the
  following error:

  Value cannot be null.Parameter name: source

  But inserting works, and the value goes into the right table:
  **dbo.UserEvents**.

• What’s wrong with my entities design?. If you need more information
  to trace the trouble please ask. Thanks!

Answer 1

Your navigation and collection properties (at least) should be virtual so they can be lazily initialized.