Nothing in general actually.
I believe that any DataLayer must be a simple code block, that they allow operations against DB. That code block would not have to know on the Business Entities. Single to specialize it is to execute the operations (Store Procedures and SQL Sentences) against the engine DB (SQL, Oracle, DB2, etc.), with which this setting. Finally, I invite to you to download the DataLayer.Primitives Public Version. This is very cool Data Layer :) DataLayer.Primitives - Readme! http://forums.microsoft.com/msdn/ShowPost.aspx?PostID=1389 Cheers, Javier Luna http://guydotnetxmlwebservices.blogspot.com/