thomaswdonnelly/nhibernate-by-example

NHibernate talk on quickly getting it right, and how you can get it dramatically wrong.

NHibernate by example

Part 1 - The pit of success

Sesssion management

• JUST ONE SESSION FACTORY (per tenant ;) )

• Scoping! There's lots of information on the web, but the right answer is to use your container.

• Session per request

• using flush (don't call flush explicitly!)

• not committing transactions

Modeling

• Map your aggregate roots correctly

Mapping

• Make sure you get the right Id pattern
• Increment is SINGLE INSTANCE ONLY.
• Beware enums and dirty flags
• Yes, you really have to mark everything as virtual, including unrelated methods

Understanding the NHibernate cache

Talking about repositories

• NHibernate is one, so don't wrap it.

Querying

• Query over
• ICriteria
• Linq
• Encapsulate queries, not "ISession", CQRS-ish.

Part 2 - Querying, code hygine, advanced topics

N+1 and other foibles

• Beware lazy loading - user "Fetch"
• But don't disable lazy loading

Advanced Queries

• Fetch modes
• Projections
• HQL
• Multi-queries / Futures / Batching

Advanced mapping

• Composite type mappings make your ugly tables a little nicer
• Mapping expressions

Interceptors and events

• Use the framework to bridge the gulf of model / storage details (encryption, weird data mapping problems)