I'm looking to port a project from our custom O/R persister to NHibernate. We currently use attributes to map our objects and fields, and I noticed that the NHibernate contrib package has something similar.

Using attributes would ease the port but I'm wondering how much of the mapping functionality the attributes cover. Do the attributes cover all the standard XML mappings?

The library doesn't have 100% coverage of the current XML tags. However, the major items are covered. Let us know which ones you may need. The are pretty easy to add into the library.

NHibernate provides a superset of the functionality of our customer mapper, so as long as we can decorate object fields (not properties) with attributes and have them persisted, as well as the various collections (many-many, many-one, one-one) we should be good. I don't think we require any of the more exotic functionality yet.

Currently, the library supports placing [Property()] attributes on properties only. However, these properties can be private, internal or public. You can also provide a custom access strategy using the Access and AccessType settings on the PropertyAttribute class.

In a nutshell, you cannot currently assign these attributes the the fields of your objects. They must be associated with a property, even if the property isn't used to accessing the underlying data fields.

The NHibernate.Mapping.Attributes.IdAttribute class doesn't seem to support choosing the "native" generator. I like the ability to specify "native" in the xml file because it allows persisting to a wide variety of database backends, and would hate to give that flexibility up in order to have the convenience of the Attributes. Can this be implemented?

It seems not-null is totally unavailable through the attributes as well.

Since we are restricted to using only .NET-defined types, it seems that StringClob isn't a type we can use while using just Attributes as well. I am trying to save large XmlDocuments by persisting their OuterXml property. The simple String type is insufficient, because even when I set the length to some long value, an nvarchar(255) is all I get. But if I use StringClob with the same length, everything works.

So, can we get support added for StringClob through the attributes? Or better yet, get StringClob automatically output instead of just "string" when the string length is obviously too long for NHibernate to persist as a string.