NHibernate on .Net 2.0Part II
time to read 2 min | 317 words

My first attempt in using generic collections in NHibernate was to just make NHibernate grok my custom collection. I took a look in the code, and it seemed rather straightforward to do so. I posted to the developer list and got the following response from Sergey, the lead developer:

  1. Have your collection class implement an interface (class MyCollection: IMyCollection)
  2. Create NHibernate-specific wrapper class (PersistentMyCollection : PersistentCollection, IMyCollection) which functions as a proxy for the real collection. All methods from IMyCollection that PersistentMyCollection implements have a Read() or Write() at the beginning, and then delegate to the real collection. PersistentMyCollection should also implement some abstract methods from PersistentCollection, these mostly have to do with snapshots and loading process.
  3. Create MyCollectionType which will derive from PersistentCollectionType and implement methods like Wrap (wrapping MyCollection in PersistentMyCollection), Instantiate, Add and Clear, and the rest.
  4. Modify the binder to accept your collection type, and that should be it.

It's straightforward but a long process, and it involves some deep knowledge about the way NHibernate works. Luckily I managed to get it most of it pre-baked by transforming the existing Set collections to use generics. I started to run into problems when I had to dynamically construct generic types, but this article sums it pretty well. I could get the correct info and get it to work.

I decided to wait with that for now, and try a less invasive approach. I'm currently trying to get it to work using a Property Accessors. I'll post my results when I'm done.

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More posts in "NHibernate on .Net 2.0" series:

  1. (01 Oct 2005) Part IV - The Sucess
  2. (01 Oct 2005) Part III
  3. (30 Sep 2005) Part II
  4. (30 Sep 2005) Part I