Hello,

I want to make sure that Hibernate is using the System.Collections.Generic.List<Element> because I'm serializing the info across the wire, etc.

Anyway, I thought I could use the collection-type attribute to achieve this. But I think I'm messing up my mapping somehow.

Here is what I have:

<bag name="Elements"
table="SomeTable"
collection-type="System.Collections.Generic.List`1[[Namespace.Element,Namespace]],System.Collections.Generic"
cascade="all-delete-orphan"
generic="true"
fetch="join"
inverse="true"
lazy="false">
<key column="key"/>
<many-to-many column="id" class="Namespace.Note, Namespace"/>
</bag>

Sorry I had to change the table name, etc. But please note the mapping works fine if I remove collection type.

Thanks.

System.Collections.Generic is in the System assembly

System.Collections.Generic.List`1[[Namespace.Element,Namespace]],System

What's the error you're getting?

Also, bag uses IList, so I don't know if you're especially gaining anything by specifying List explicitly

That was a nice catch, but I'm still getting the same problem.

You know, I'm getting a generic error: telling me that it can't parse my mapping file.

"Could not compile the mapping document: Namespace.Element.hbm.xml"

Thanks!

OK, I had a problem in my mapping I changed it assembly to mscorlib.

Now I get a different exception:

{"Custom type does not implement UserCollectionType: System.Collections.Generic.List`1[[HibernateTest.Element, HibernateTest.MeetingDAL, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]"}

Does this mean that hibernate cannot give me a List<T>? It will only give me types that implmement a bunch of nhibernate interfaces?

Thanks.

Hello,

could someone please tell me if what I'm doing is possible, but I'm making a syntax error.

Or what I'm doing is not possible. ;-)

Thanks!

No, what you are doing is not possible.

Thanks sergey!

Hi h1!

AFAIK, there is no way to get pure List<SomeClass> from NHibernate – only PersistentGenericBag<SomeClass> or an instance of another NHibernate aware collection (PersistentGeneric***<SomeClass> are built-in ones). You may even create your own collection (sample is in "\src\NHibernate.Test\UserCollection" – it is for non-generic collection, but it is not so hard to make it generic). The real problem is that you have to define “special” collection – one that will implement IPersistentCollection interface – to make NHibernate work. Another option is to use one of the built-in classes (PersistentGeneric***) but it is really unreasonable as you’ll get all the same stuff you have with built-in collections.
collection-type attribute must point to special helper class (it is even not a collection class at all!) that will tell NHibernate how it can make use of your own collection classes (either just one “pure” collection, or both of them “pure” collection and “persistent” collection.
I suppose it may be handy to “extend” built-in types (for example to implement IBindingList interface in persistent collection and have ListChanged event there), but not to “shrink” these classes to simple plain List<SomeClass>. BTW maybe you can extend collection to add “smart” serialization capabilities to it (serialize just what you need, excluding all the NHibernate internal stuff) – but I suppose it is easier to do outside of NHibernate.

2 Sergey
Maybe I’m missing something obvious, but do I have to implement my own PersistentGenericBag class (probably a BindingList<T> descendant, or a kind of wrapper?) to have IBindingList capabilities in persistent collections. I tried to wrap NHibernate collection into BindingList<T> in my class property setter, but it force NHibernate to retrieve all the collection – not a behaviour I want to have. Is it possible in principle to have “lazy” collection, which will implement IBindingList interface?

Since it's BindingList that's forcing NHibernate to load the collection, there isn't much NHibernate could do about that. So yes, you will have to write your own IPersistentCollection implementation.