Protect a list from the undesired Add leaving Entity Framework happy

Question

I have an object, say the usual Order that have a collection of LineItem. To satisfy some business rules I need to have complete control against the list (i.e. nobody can add an element to this list simply using the built in Add() method). So I do something like:

public class Order {
    private List<LineItem> lineItems {get; set;} 

    public IEnumerable<LineItem> LineItems {
        get { return lineItems.AsReadOnly(); }
    }
}

This solution do the job but have a big side effects if other player come into play (e.g. Entity Framework). In fact during the model building, EF expects an ICollection (while I need an IEnumerable):

modelBuilder.Entity<Order>()
            .HasMany<LineItem>(e => e.LineItems) // here is the exception: No implicit conversion among IEnumerable and ICollection
            .OtherMappingProperties(); // <-- this don't belong to EF's Fluent API :)

EDIT 1 - The solution provided by @Pieter21 avoid the compile time error, since LineItem is now a Colection, but I get a runtime exception when somewhere in my code I have something like:

return Set.Include(s => s.LineItems)

since none have set lineItems (none could since is private) so I get a NullPointerException. Since the Entity configuration and Domain model are in different package the use of internal instead of private would not resolve the problem unless the use of InternalsVisibleTo (but I don't want to spoil the AssemblyInfo.cs of the Domain model with something persistence related)

How to workaround this issue?

PS: The EF configurations and domain model are in different namespaces.

possible duplicate of [Entity Framework read only collections](http://stackoverflow.com/questions/11191103/entity-framework-read-only-collections) — Gert Arnold, Sep 16 '14 at 09:23

score 0 · Answer 1 · edited Sep 16 '14 at 10:49

0

Can you do something like:

        public ICollection<LineItem> LineItems 
        {
            get 
            { 
                return new ReadOnlyCollection<LineItem>(lineItems); 
            } 
        }

edited Sep 16 '14 at 10:49

BAD_SEED

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answered Sep 16 '14 at 08:27

Pieter21

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I can't do `return Set.Include(s => s.Items);` since `lineItems` is `null` and I get a NullPonter! – BAD_SEED Sep 16 '14 at 10:42
That's an initialization/constructor problem, not a EF/mapping problem. – Pieter21 Sep 16 '14 at 10:51
1

@Pieter21 How would you map `LineItems` and at the same time make EF populate `lineItems`? I don't think this can work. – Gert Arnold Sep 16 '14 at 11:17

Protect a list from the undesired Add leaving Entity Framework happy

1 Answers1