A property with a collection type of for example -> public class MyCollection : PersistentGenericBag<MyEntity> can now be mapped using the Mapping By-Code.

Previously, mapping a non-generic custom collection class which inherits PersistentGenericBag<> or other generic NHibernate collection class, made the ModelMapper throw a NotSupportedException:

"Can't determine collection element relation (property MappedProperty in MyType)"

Root cause for this was the Type extension method DetermineCollectionElementType was not willing to find the element type of a collection type, if the collection type itself wasn't generic. (Even if it did inherit IEnumerable<>)