Hibernate version:1.2
Name and version of the database you are using: SQL Server 2005

I’ve got a mapping problem that I’m hoping someone can help me with. At the database level we have this structure:

PartyRole
PartyRoleID (PK)
PartyRoleTypeID

PartyRelationship
PartyRelationshipID (PK)
ConsumerPartyRoleID (FK)
PartyRelationshipTypeID
ProducerPartyRoleID (FK)
...

As you can see from this the PartyRelationship links two PartyRoles, and each PartyRole can be involved in multiple relationships.

In the domain we were hoping to represent it as the PartyRole having two dictionaries:

private IDictionary<PartyRelationshipKind, IList<PartyRelationship>> _producerRelationships;
private IDictionary<PartyRelationshipKind, IList<PartyRelationship>> _consumerRelationships;

The dictionary is indexed by the PartyRelationshipTypeID (from the PartyRelationship table) and the value should be the collection of relationships of that type that the role is involved in.

We wanted to use a dictionary rather than an IList as we thought it could be faster. For example if you want all the relationships of type X that the role is involved in we don’t want to have to load up and then iterate through all of the relationships, as it could be quite costly.

The problem is that there is no obvious way to map this, I’ve tried this:

<map name="ProducerRelationships" cascade="none" access="nosetter.camelcase-underscore" generic="true" lazy="true">
<key column="ProducerPartyRoleID" />
<index column="PartyRelationshipTypeID" type="PartyRoles.PartyRelationshipKind, Parties.Domain"/>
<one-to-many class="PartyRelationship" />
</map>

Unsurprisingly this doesn’t work, I’m expecting NHibernate to understand that the key column (ProducerPartyRoleID) will bring back multiple values of type PartyRelationship which should be put in a list and stored in the dictionary. When I run code with this mapping I get this sort of error:

NHibernate.MappingException: Unknown entity class: System.Collections.Generic.List`1[[PartyRoles.PartyRelationship, Parties.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].

So what I’m wondering is whether there is a way to do this?

I'm also interested in this issue, since I've just the same 'structure'. (A dictionary containing another dictionary).
However, I've worked around this, by creating another class, which holds the other List.
So, instead of this:

I have done this

where the ItemCollection class, contains another List.

But now however, I experience another problem with this; when I run my program, NHibernate complains that it could not compile the mapping document.
It says 'error mapping generic collection ... expected one generic parameter, but found 2' :(

I've added a JIRA issue for this:

http://jira.nhibernate.org/browse/NH-1065

I have a similar problem too.

In the database I have the following tables:

Person <- PersonAddress -> Address

A person can have several addesses, so PersonAddress links a person to an address with the type of address, and dates that the address was valid.

In the domain model, my person class contains a dictionary, with the address type as the key and an AddressTemporalCollection object as the value. The AddressTemporalCollection object also contains a dictionary, with the start date of the address as the key, and the address as the value.

Is it possible to map nested collections such as this?

very usefull for us…thanks.


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