Hey guys,

I have a tricky question. I have an object that uses a GUID as unique identifier. I know about the unsaved-value attribute in the mapping file.

In my application, the GUID is already set because it comes from an external system. Therefore, NHibernate does not know that this is a new object. Only my application or the domain object can know that (e.g. with a flag).

I'm wondering how I can tell NHibernate on the first SaveOrUpdate call to save the object rather than update it.

Thanks, Christoph

Well, you can call either Save or Update yourself, without relying on SaveOrUpdate. Another possibility is to use a version field, new objects would have it set to 0 or some other default, and existing objects will have a different value.

Found the problem :-)

I used "guid" instead of "generated" for the generator algorithm.

Thanks, Christoph

Personally, I'd like to see NHibernate have some interface (IAssignedIdentifier???) with a "bool IsNew" property.

ISession.SaveOrUpdate() would check to see if the object it is saving is an IAssignedIdentifier (bad name, I know) and if so, check IsNew.

This would let you override the UnsavedValue behavior for assigned IDs and other situations where it might come up instead of having to manually choose between Save or Update in your code.