Lazy load an ICompositeUserType - nhibernate

Question

I have a class MoneyCompositeUserType : ICompositeUserType
Which I use like so in a mapping:
public InvoiceMap()
{
Table("Invoices");
Id(x => x.Id);
Map(x => x.Customer);
Map(x => x.Number);
Map(x => x.TotalValue)
.CustomType(typeof(MoneyCompositeUserType))
.Columns.Clear()
.Columns.Add("TotalValue_Amount", "TotalValue_Currency");
}
And here is the class:
public class Invoice
{
public virtual int Id { get; set; }
public virtual int Number { get; set; }
public virtual string Customer { get; set; }
public virtual Money TotalValue { get; set; }
}
I thought that the value would be lazy loaded, that's the point of the virtual right? But the NullSafeGet method of the composite user type is called when the item is loaded. Here is my failing test:
using (var session = NHibernateHelper.OpenSession())
{
var fromDb = session.Get<Invoice>(invoice.Id);
Assert.IsFalse(NHibernate.NHibernateUtil.IsPropertyInitialized(fromDb, "TotalValue"));
}
Why is that property not being lazy loaded?

Answer 1

I thought that the value would be lazy loaded, that's the point of the virtual right?
Not exactly -- NHibernate needs your properties to be virtual so that it can use a proxy class in place of your class to enable lazy loading. Lazy loading is not enabled just because a property is marked virtual.
I believe all you should have to do is mark the individual property with .LazyLoad in your mapping (see lazy properties for more information):
Map(x => x.TotalValue)
.LazyLoad() // <-----
.CustomType(typeof(MoneyCompositeUserType))
.Columns.Clear()
.Columns.Add("TotalValue_Amount", "TotalValue_Currency");