Hi, To support the order-by attribute in collection mapping, NHibernate uses the OrderedSet class from Iesi.Collections. Unfortunately there is no corresponding ordered set class available in the BCL in .Net 4.
I have implemented a new OrderedSet based on ISet<T>, etc. from .Net 4, but now I'm not sure where to put it. Option 1 Put it as e.g. NHibernate.Collections.Generic.OrderedSet. We will have no remaining dependency on Iesi.Collections. But some users prefer to avoid referencing NHibernate types directly from e.g. domain logic. Option 2 Do a rework of Iesi.Collections targeting .Net 4 with breaking changes: Remove all classes now covered by the BCL. Remaining classes (such as OrderedSet) would have their interfaces updated to match .Net 4 interfaces. The current version is likely to be cumbersome in combination with .Net4 anyway, due to naming conflicts. This would be similar to what C5 did: http://www.itu.dk/research/c5/ and http://www.itu.dk/research/c5/c5-rasmus-nielsen-2011-05-25.pdf What do you think? /Oskar
