I recently delivered a presentation at North Houston Dot Net User Group regarding NHibernate and some Advanced ORM Topics. I covered several topics related to NHibernate and ORMs in general:

• Data Impedance Mismatch
• Impedance Mismatch Sources
• Problem Domains
• Data Persistence
• Impedance Mismatch Reduction
• Persistence Ignorance
• Lazy Loading
• Difference between “Heavy-Weight” and “Light-Weight” ORMs

And of course, I discussed some of the various options besides NHibernate that are available to Developers:

• Entity Framework
• Telerik OpenAccess
• CODE Framework Business Objects
• PetaPoco
• etc.

Finally, we demo’d  several ways in which NHibernate could be used – primarily focusing on the basic CRUD operations.

My conclusion in the presentation was that at EPS \ CODE Consulting, we tend to avoid NHibernate due to the amount of XML configuration and maintenance that is required. However, it is a popular choice among many developers, and is a useful tool to have in the “toolbelt”, as it were. Additionally, it can be very useful for interfacing a newer UI with an older Database, as there are many NHibernate plugins available that interface to databases that are not available in some of the newer ORMs. Examples we discussed at the meeting included DBase or Clipper databases, or possibly older Fox databases.

Obviously, the preference is to migrate these to SQL Server, or some other modern database platform – but that may not always be an option. If not, NHibernate may be the right choice.

References:

Code Download for Presentation:

• NHDNug NHibernate

Impedance Mismatch discussions