DataObjects.NET 4.0

DataObjects.Net v4.0 is a comprehensive business logic layer development framework providing it with: Storage independent data access layer - probably the most independent one. It supports not just SQL databases, but generally any storage that can be classified as indexing engine. Object-relational mapping framework providing completely transparent persistence - we've gone even further than with v3.9 here. We support arbitrary Keys, persistent Entities, Structures and EntitySets.

Go to http://www.x-tensive.com/Products/DO/Default.aspx

See also these related projects.