NHibernate Many-to-many

Question

Hi Guys.

I have a legacy database and I am trying to create a Nhibernate DAL. I have a problem with a mapping on Many-To-Many table.

The Database tables is like this. studio_Subscribers studio_Groups (contains a IList of Subscribers) studio_Subscribers_Groups - Many-To-Many table with primary keys

The problem is when I create a SubscriberGroup instance and fill it with Subscribers they gets saved to the studio_Subscribers table but not to the Many-To-Many table.

I cant figure out whats wrong?

Thanks in advance. /Johan

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                    assembly="Meridix.Studio.Common"
                    namespace="Meridix.Studio.Common">
    <class name="SubscriberItem" table="studio_Subscribers">
        <id name="StorageId" column="Id" unsaved-value="0" access="nosetter.camelcase">
            <generator class="identity" />
        </id>
        <property name="Id" column="DomainId" not-null="true" />
        <property name="Subscriber" column="Subscriber" not-null="true" length="50" />
        <property name="Description" column="Description" not-null="false" length="100" />
        <property name="Type" column="Type" not-null="true" length="40" type="Meridix.Studio.Data.Repositories.EnumStringTypes.SubscriberTypeEst, Meridix.Studio.Data.Repositories" />
    </class>
</hibernate-mapping>



<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
                    assembly="Meridix.Studio.Common"
                    namespace="Meridix.Studio.Common">
    <class name="SubscriberGroup" table="studio_Groups">
        <id name="StorageId" column="Id" unsaved-value="0" access="nosetter.camelcase">
            <generator class="identity" />
        </id>
        <property name="Id" column="DomainId" not-null="true" />
        <property name="Name" column="Name" not-null="true" length="200" />
        <property name="Description" column="Description" not-null="false" length="300" />

        <bag name="Subscribers" table="studio_Groups_Subscribers" access="nosetter.camelcase">
            <key column="GroupId"></key>
            <many-to-many column="SubscriberId" class="SubscriberItem" />
        </bag>
    </class>
</hibernate-mapping>

Answer 1

Shouldn't you have an appropriate bag on your subscriber aswell with a many-to-many relation to the group?

<bag name="Groups" table="studio_Groups_Subscribers" access="nosetter.camelcase">
        <key column="SubscriberId"></key>
        <many-to-many column="GroupId" class="GroupItem" />
</bag>

and maybe have a cascade="save-update" on your SubscriberItems collection so that saving the Group will update your children with the appropriate relation from "the other side".

Answer 2

Thanks for your answer, but it didnt help, I still cant get the relation to be persisted in the Many-To-Many table. Its stange beacause if i add an unsaved item to a new unsaved group and saves the group, the group and the subscriber are saved in their tables but the Relation is not?

Any ideas?

/Johan

Answer 3

I believe it is to do with the cascade options, check out Ayende's post on it and I imagine with a bit of Googling you can find the correct syntax to go into your hbm file. I use fluent-NHibernate so I can't help you with the XML file.

http://ayende.com/Blog/archive/2006/12/02/NHibernateCascadesTheDifferentBetweenAllAlldeleteorphansAndSaveupdate.aspx