WCF and NHibernate

That is your problem. You can't expose non serializable types as part of a service contract. You have two options to work around this:

1. Create a data contract that looks like the types you want and expose those in the service contract. As messages come in, you can map the facade type to the nhibernate type before processing at your business tier. As messages are returned you can control mapping the nhibernate type to the new data contract type before returning to clients. The clients sees the same type essentially. Pros: you can let the service model handle serialization for you. Cons: the service model deserializes the stream to a type that you subsequently will throw away once you map to nhibernate...so that creates overhead.
2. An alternative, better performing, is IXmlSerializable types. This way, the service model gives you a chance to handle the XML read and write process for your nhibernate types. Create a wrapper type like "PersonSerializer" that implements IXmlSerializable, then override read/write to handle XML stream directly. Pros: less overhead and direct control over schema generation. Cons: you have to work with XML directly.

For a sample on #2 read my chapter 2 on www.thatindigogirl.com. I have extensive discussion on serialization in there, and an IXmlSerializable example.

MicheleLerouxBustamante at 2007-8-31 >