Hello,

I'm still fairly new to NHibernate, and we are attempting to build an application which allows many-to-many associations between several entities. My question is, what's the best way to accomplish this in the mapping? Has anyone else tried this or can direct me to a sample app with similar parameters?

Below, I'll attempt the describe the key areas of what we have. So far, I've found that I have to use not-found="ignore" because NHibernate enforces referential integrity. Also, using the cascade features seem unreliable for updates in this situation (possibly due to my mappings). Right now, I create and insert each object and then create and insert the association, and this works fine. But I would prefer to use the cascade features if I could.

Thanks in advance for your help.

Here's the table structure. It's hosted on MSSQL2005. All Id fields are GUID's:

[Association]
ParentId
ChildId

[Person]
Id

[Location]
Id

[Document]
Id

Each POCO classes looks something like this:

class Person{
Guid Id {get;set;}
IList<Person> Persons {get;private set}
IList<Location> Locations {get;private set}
IList<Document> Documents{get;private set}
}

Below is a mapping file for the Person entity:

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Model" namespace="Model.DAO">
<class name="Person">
<id name="Id" type="System.Guid" column="Id">
<generator class="guid.native"/>
</id>

<bag name="Persons" table="Association">
<key column="ParentId"/>
<many-to-many class="Person" column="ChildId" not-found="ignore">
</bag>

<bag name="Locations" table="Association" cascade="none">
<key column="ParentId"/>
<many-to-many class="Location" column="ChildId" not-found="ignore"/>
</bag>

<bag name="Documents" table="Association" cascade="none">
<key column="ParentId" />
<many-to-many class="Document" column="ChildId" not-found="ignore"/>
</bag>


</class>

</hibernate-mapping>