NHibernate : map to fields or properties?

Question

When you create your mapping files, do you map your properties to fields or properties :

Answer 1

Null Objects

Mapping to fields can be useful if you are implementing the null object pattern if your classes. As this cannot be performed (easily) when mapping to Properties. You end up having to store fake objects in the database.

HQL

I was unsure that with HQL queries you had to change the property names if you were using a field access approach. ie if you had I thought you could still write "From Person where FirstName = :name"; as it would use the property name still.

Further discussion on field strategies and Null object can be found here.

Performance

In relation to performance of field vs property on John Chapman's blog It appears there isn't much of an issue in performance with small-midrange result sets.

In summary, each approach has certain perks that may be useful depending on the scenario (field access allows readonly getters, no need for setters, property access works when nothing special is required from your poco and seems to be the defacto approach. etc)