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Asked: 2026-05-11T04:12:49+00:00

I have a problem. Imagine this data model: [Person] table has: PersonId, Name1 [Tag]

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I have a problem. Imagine this data model:

[Person] table has: PersonId, Name1   [Tag] table has:  TagId, TagDescription   [PersonTag] has: PersonId, TagId, IsActive

Since [PersonTag] isn’t just a simple many-to-many join table, I have all three entities created in nHibernate (exactly like they are in the data model). PersonTag, therefore, needs a composite-id, which I have mapped to a class like this:

<composite-id name='PersonTagKey' class='PersonTagKey'>   <key-property name='PersonId'></key-property>   <key-property name='TagId'></key-property> </composite-id>

I want to traverse the object graph and be able to look at both the Person and Tag objects from a retrieved PersonTag object. So, I have properties on the PersonTag object to do that, mapped like this:

<many-to-one name='Person' column='PersonId' lazy='proxy' cascade='none' class='Person'/> <many-to-one name='Tag' column='TagId' lazy='proxy' cascade='none' class='Tag'/>

When I try to create a PersonTag object and save it, I get an ‘Invalid index n for this SqlParameterCollection with Count=n’ error. I know this is because I’ve mapped the PersonId and TagId properties twice, once for the composite-id, and once for the many-to-one relationship. If I don’t map the many-to-one objects, then everything works fine.

Is there some way for me to be able to have a composite-id AND a many-to-one relationship based on the same column modeled in the same nHibernate entity?

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1 Answer

  1. Kay, here’s the answer. Little-to-no documentation on this:

    <composite-id name='PersonTagKey' class='PersonTagKey'>    <key-many-to-one name='Person' column='PersonId' lazy='proxy' class='Person'>   <key-many-to-one name='Tag' column='TagId' lazy='proxy' class='Tag'/> </composite-id>

    This will allow you to create a composite-id made up of the inverse of a many-to-one relationship.

    Good hunting…

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