NHibernate GenericADOException

Question

sesion.Get(id); produces sometimes a GenericADOException:

could not load an entity: [PFC__ Servidor.Entidades.Usuario#10][SQL: SELECT usuario0 .us_id as us1_1_0_, usuario0_.us_email as us2_1_0_, usuario0_.us_contrasena as us3_1_0_ FROM public.usuario usuario0_ WHERE usuario0_.us_id=?]

Any known where is the problem? Why not always fails?

PD: Sorry for my english.

ACT1: Inner exception: [System.NullReferenceException] "Object reference not set to an instance of an object"

Answer 1

Can you post the innerException?

• Are you sure your connectionstring is wellformed?
• Are you sure your database has been created?
• Are you sure your mapping file point at right table name?
• Are you sure your database instance is running?

update

I also found this:

Could not load an entity when table is existing

Answer 2

sometimes

Is your session shared among threads? If so, death. Sessions are not thread safe.

Answer 3

I had this issue when I started implementing the current framework. It is in fact as Jason is suggesting - you need to set your NHibernate session scope to per-request. This means a new session will be opened for each request and closed at end of request. However, you only create the session factory once per application start since this is the most expensive part.

Are you using any dependency injection? You can find great examples on how to achieve per-request session scoping on Windsor Castle NHibernate facility .

If you are doing it manually however, you can open an NHibernate session in your Global.asax Request_begin and ensure it is closed and disposed in Request_End method.

A neat way to work with NHIbernate is:

• Castle Windsor (dependency injection)
• Repository pattern (separate your data access)
• Unit of work pattern. Instead of injecting nhibernate session you inject correct repository and unit of work into services
• Service layer (business logic) - what you call from your controllers or application presentation layer