Question

Given a database that has numerous repeating columns used for auditing and versioning, what is the best way to model it using NHibernate, without having to repeat each of the columns in each of the classes in the domain model?

Every table in the database repeats these same nine columns, the names and types are identical and I don’t want to replicate it in the domain model.

I have read the docs and I saw the section on inheritance mapping but I couldn’t see how to make it work in this scenario. This seems like a common scenario because nearly every database I’ve work on has had the four common audit columns (CreatedBy, CreateDate, UpdatedBy, UpdateDate) in nearly every table. This database is no different except that it introduces another five columns which are common to every table.

Answer 1

This can be accomplished by using the component element in the mapping file.

The basic idea is to create a class to hold the common properties and reference it from each of the entities in your model.

Then inside your mapping file add a reference to this property like this…

<component name="RecordMetadata" class="RecordMetadata" insert="true" update="true">
    <property name="UpdatedBy" />
    <property name="UpdatedDate" />
    <property name="CreatedBy" />
    <property name="CreatedDate" />
</component>