April 9, 2010

NHibernate 2.1 throws System.InvalidCastException on Oracle 10g R1 client

Filed under: Development — Tags: , — Darrin Maidlow @ 3:52 pm

When deploying an early build of an up and coming product on a customers machine I came across the following error:

System.InvalidCastException: Unable to cast object of type ‘Oracle.DataAccess.Client.OracleConnection’ to type ‘System.Data.Common.DbConnection’

This was one of those awesome “doesn’t happen on any of my machine” errors.  After some mucking around we determined that the client machine was using the Oracle 10g  R1 client.  The machines and VMs here we used for testing were all running either 11g, or 10g R2.  Doh!

The simple resolution to this was to modify the NHhibernate config and add the following property:

   1: <property name="hbm2ddl.keywords">none</property>

Depending on your underlying databases and mappings this could cause problems with your code project.  Hopefully you’re not using reserved words, or bad Oracle syntax =).

Under the hood, the problem seems to be that the Oracle10gDialect does not provide an implementation of IDataBaseSchema for 10gR1.   Fabio Maulo has provided some sample code and the steps on for your database and submit it to the NHibernate project for inclusion.

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