Hierarchical entity parent key in NHibernate ByCode - nhibernate

Question

Using NHibernate 3.2 ByCode configuration, I am attempting to map the following hierarchical entity:
public class BusinessType
{
public virtual Guid BusinessTypeId { get; set; }
public virtual Guid? ParentBusinessTypeId { get; set; }
public virtual String BusinessTypeName { get; set; }
public virtual ICollection<BusinessType> Children { get; set; }
}
with this ClassMapping:
public class BusinessTypeMapper : ClassMapping<BusinessType>
{
public BusinessTypeMapper()
{
Id(x => x.BusinessTypeId, x => x.Type(new GuidType()));
Property(x => x.ParentBusinessTypeId, x => x.Type(new GuidType()));
Property(x => x.BusinessTypeName);
Set(x => x.Children,
cm =>
{
// This works, but there is an ugly string in here
cm.Key(y => y.Column("ParentBusinessTypeId"));
cm.Inverse(true);
cm.OrderBy(bt => bt.BusinessTypeName);
cm.Lazy(CollectionLazy.NoLazy);
},
m => m.OneToMany());
}
}
This works fine, but I'd rather be able to specify the key of the relation using a lambda so that refactoring works. This seems to be available, as follows:
public class BusinessTypeMapper : ClassMapping<BusinessType>
{
public BusinessTypeMapper()
{
Id(x => x.BusinessTypeId, x => x.Type(new GuidType()));
Property(x => x.ParentBusinessTypeId, x => x.Type(new GuidType()));
Property(x => x.BusinessTypeName);
Set(x => x.Children,
cm =>
{
// This compiles and runs, but generates some other column
cm.Key(y => y.PropertyRef(bt => bt.ParentBusinessTypeId));
cm.Inverse(true);
cm.OrderBy(bt => bt.BusinessTypeName);
cm.Lazy(CollectionLazy.NoLazy);
},
m => m.OneToMany());
}
}
The problem is that this causes NHibernate to generate a column called businesstype_key, ignoring the already-configured ParentBusinessTypeId. Is there any way to make NHibernate use a lambda to specify the relation, rather than a string?

Answer 1

I never need to navigate from children to parents, only from parents
to children, so I hadn't thought it necessary
then remove public virtual Guid? ParentBusinessTypeId { get; set; } completly. NH will then only create "businesstype_key" (convention) and no "ParentBusinessTypeId". if you want to change that then you have to specify your prefered columnname with cm.Key(y => y.Column("yourpreferredColumnName"));