Nhibernate - Map a single row table

I have an existing nhibernate web application and I'm about to add a configuration table that will contain all system wide configuration options. This table will always contain one and only one row. Each column will contain one configuration property. I plan on having a domain object that will have a matching property for each column in the table. The users wil开发者_如何学编程l be able to modify the values for each property in an admin screen. I plan on populating the table with one row during installation, setting initial values for each configuration option. My questions are as follows:

1) I only want the system to update the existing row, and want to block any deletes or inserts on the table. I can, of course, enforce this by not creating application tier functions that do deletes or updates, but I wondered if NHibernate had some built in mapping or configuration options to help. I'd prefer to not have to do this at the database level since we are writing a database agnostic application, and so far, have not had to write any database platform specific code or scripts.

2) Would the mapping be different for this class than my other "normal" classes?

Answer to 1) NHibernate does not have any "configuration" that will enable to block "inserts" and "deletes" only. You can do work arounds e.g. Write an your own PreDeleteEventListener and PreInsertEventListener and stop updates and inserts if the entity is your configuration entity.

However I would advise you do to enforce this configuration via the application i.e. the configuration repository should only expose an Update" function and no more.

Answer to 2) I am assuming that this table does not have a primary key (as it is the only row in the table). As far as Im aware, NHibernate cannot work with entities that do not have primary keys. You may have to add a primary key just to get it to work for NHibernate