FIXED: "Invalid type owner for DynamicMethod" error in Nhibernate

If you recieve the "Invalid type owner for DynamicMethod" error while initializing you NHibernate SessionFactory then it's pretty likely that you are using generic methods on some of your lazy loaded/proxied classes.

Nhibernate incorporates a reflection optimization that speeds up the creation of proxy classes. This reflection optimization does not play well with generics. The error it throws is "Invalid type owner for DynamicMethod". Not very friendly.

So, to fix this you must either stop using generic methods OR turn off the optimization. To turn off the optimization you must run the following code before you initialize your SessionFactory.

NHibernate.Cfg.Environment.UseReflectionOptimizer = false;

Making the leap to QueryOver

So, if you are using the ActiveRecord/NHibernate stack I highly recommend switching to query over. The syntax is cleaner and it's type-safe.

Here is an example of a criterion based query:


Here is an example of the same query in QueryOver:



Unlike the Linq language for Nhibernate QueryOver is just a translation layer for Criterion.