Fluent NHibernate Generated AND Assigned ID Columns
I'm using Fluent NHibernate for my data-persistence in a web application.
My problem... I have a base class that maps all entities with an ID property of type T (almost always an int or GUID) using GeneratedBy().Identity()
On application start-up, I have a boot-strapper that checks and verifies the needed seed-data is populated. My problem is, some of the seed-data that is populated needs a specific ID. (IDs that would correspond to an enum or system user)
Is there any way to force NHibernate to commit the record using the ID that I specify, rather than an auto-generated one? Any other commits to the repository thereafter can be auto-generated.
Answer
Id(x => x.Id).GeneratedBy.Assigned();
If you want the application to assign identifiers (as opposed to having NHibernate generate them), you may use the assigned generator. This special generator will use the identifier value already assigned to the object's identifier property. Be very careful when using this feature to assign keys with business meaning (almost always a terrible design decision).
Due to its inherent nature, entities that use this generator cannot be saved via the ISession's SaveOrUpdate() method. Instead you have to explicitly specify to NHibernate if the object should be saved or updated by calling either the Save() or Update() method of the ISession.
http://nhibernate.info/doc/nhibernate-reference/mapping.html#mapping-declaration-id-assigned