Finding source of duplicate mappings in Fluent NHibernate

Question

Earlier today, I broke one of my classes into two, by marking the original as abstract, and creating two subclasses that inherit from the abstract base.

I added a line to my FluentNHibernate mapping to discriminate the subclasses based on a column value (table-per-class heirarchy) as follows:

DiscriminateSubClassesOnColumn("EntryType");

That field is an integer in the database.

My new mappings inherit from

SubClassMap<MyChildType>

With a new line in the constructor method of MyChildTypeMap for the discriminator as follows:

DiscriminatorValue(1);

I am continuously running into this exception:

"Duplicate class/entity mapping MyNamespace.MyChildObject"

In the Fluent NHibernate session builder, (Fluently.Configure()....) I added the line to export the mappings to hbm files. Sure enough, the subclass is listed twice in the mapping file of the parent class.

I am not using AutoMapped configurations. I am using Fluent NHibernate 1.2.0.0 I am using NHibernate 3.2.0.400

I'm at wit's end trying to figure out where this comes from. Can anyone help?

Have you ever figured out the root cause of this? I have a similar question on SO. — Astaar

David R. Longnecker David R. Longnecker · Accepted Answer · 2011-10-07T20:59:57

A quick way to see how your mappings are constructed is to use FluentNHibernate's diagnostics:

Fluently.Configure()
    .Database(\\your db stuff here)
    .Diagnostics(diag => diag.Enable().OutputToConsole())
    .Mappings(\\mappings);

This will stream (to your console in this case, you can also OutputToFile) a debug log of what mappings are being created from what classes and what caused them to be added or skipped.

Finding source of duplicate mappings in Fluent NHibernate

1 Answers