NHibernate bycode mapping to a protected collection

Question

I'm trying to map (by code) a protected collection to a bag but I'm struggling. e.g.

public class MyClass
{
    ....
    protected virtual ICollection<Items> MyItems { get; set; }
    ....
}

public class MyClassMapping : ClassMapping<MyClass>
{
    ...
    Bag(x => x.MyItems, map =>
    {
        ....
    }
    ...
}

It throws a mapping exception with the inner exception being "ArgumentNullException: Value cannot be null. Parameter name: localMember". It works fine if the "MyItems" collection is public.

I followed this article (https://groups.google.com/forum/#!topic/nhusers/wiH1DPGOhgU) which recommends using the method overload that takes a string. e.g.

public class MyClassMapping : ClassMapping<MyClass>
{
    ...
    Bag("MyItems", map =>
    {
        ....
    }
    ...
}

But this gives a compilation error "The type arguments for method .... cannot be inferred from the usage. Try specifying the type arguments explicitly".

Is it possible to map to a protected collection (I'm using NH 3.3)? Can someone give me an example?

Thanks, Chet

Answer 1

As we can see the overloaded method here: PropertyContainerCustomizer.cs

public void Bag<TElement>(string notVisiblePropertyOrFieldName
  , Action<IBagPropertiesMapper<TEntity, TElement>> collectionMapping
  , Action<ICollectionElementRelation<TElement>> mapping)
{ ... }

What we have to pass as the generic template is the TElement, the one used as ICollection<TElement>.

And because the defintion is:

// TElement is Items
protected virtual ICollection<Items> MyItems { get; set; }

SOLUTION: What we have to do is declare the mapping like this

// the TElement must be expressed explicitly as Items
Bag<Items>("MyItems", map =>
{
    ....
}