Nhibernate - Mapping List doesn't update List indexes - nhibernate

Question

I'm having one self-referencing class. A child has a reference to its parent and a parent has a list of children. Since the list of children is ordered, I'm trying to map the relation using NHibernate's .
This is my mapping:
<class name="MyClass">
<id name="Id">
<generator class="native"/>
</id>
<list name="Children" cascade="delete" inverse="true">
<key column="ParentId"/>
<index column="ListOrder"/>
<one-to-many class="MyClass"/>
</list>
<many-to-one name="Parent" class="MyClass" column="ParentId"/>
</class>
The problem I'm having is when having a bi-directional mapping child<->parent, the list index (ListOrder) isn't updated in the database when I do my CRUD dance. This means that when I e.g. remove a child, I get holes in the children list after saving to the database and fetching the parent again. If I remove the bidirectionality, by not having a many-to-one from the children to the parent (and no inverse=true), the ListOrder is updated correctly.
Have any of you seen this before? Is there any simple solution?

Answer 1

Yes, it's because of inverse=true, an alternate solution would be to use a set or bag instead of list with order="ListOrder", add the ListOrder column as a property to the MyClass class with an empty setter and a getter that always returns it's index from it's parent's child collection. Like this:
<class name="MyClass">
<id name="Id">
<generator class="native"/>
</id>
<bag name="Children" cascade="delete" inverse="true" order-by="ListOrder">
<key column="ParentId"/>
<one-to-many class="MyClass"/>
</bag>
<property name="ListOrder" column="ListOrder"/>
<many-to-one name="Parent" class="MyClass" column="ParentId"/>
</class>
and the class
public class MyClass
{
public virtual int ID { get; set; }
public virtual IList<MyClass> Children { get; set; }
public virtual MyClass Parent { get; set; }
public virtual int ListOrder
{
get
{
if (Parent == null || !Parent.Children.Contains(this)) return -1;
return Parent.Children.IndexOf(this);
}
set { }
}
}