Best practices for querying with NHibernate

Question

I've come back to using NHibernate after using other technologies (CSLA and Subsonic) for a couple of years, and I'm finding the querying a bit frustrating, especially when compared to Subsonic. I was wondering what other approaches people are using?

The Hibernate Query Language doesn't feel right to me, seems too much like writing SQL, which to my mind is one of the reason to use an ORM tools so I don't have to, furthermore it's all in XML, which means it's poor for refactoring, and errors will only be discovered at runtime?

Criteria Queries, don't seem fluid enough.

I've read that Ayende's NHibernate Query Generator, is a useful tool, is this what people are using? What else is out there?

EDIT: Worth a read http://www.ayende.com/Blog/archive/2007/03/17/Implementing-Linq-for-NHibernate-A-How-To-Guide--Part.aspx

Answer 1

The thing with LINQ for NHibernate is still in beta; I'm looking forward to NHibernate 2.1, where they say it will finally make the cut.

I made a presentation on LINQ for NHibernate around a month ago, you might find it useful. I blogged about it here, including slides and code:

LINQ for NHibernate: O/R Mapping in Visual Studio 2008 Slides and Code

Answer 2

To rid yourself of the XML, try Fluent NHibernate

Linq2NH isn't fully baked yet. The core team is working on a different implementation than the one in NH Contrib. It works fine for simple queries though. Use sparingly if at all for best results.

As for how to query (hql vs. Criteria vs. Linq2NH), expose intention-revealing methods (GetProductsForOrder(Order order), GetCustomersThatPurchasedProduct(Product product), etc) on your repository interface and implement them in the best way. Simple queries may be easier with hql, while using the specification pattern you may find the Criteria API to be a better fit. That stuff just stays encapsulated in your repository, and if your tests pass it doesn't much matter how you implement.

I've found that the Criteria API is cumbersome and limiting but flexible. HQL is more my style (and it's better than SQL - it's object based, not schema based) and seems to work better for me for simple GetX methods..