Communication between BLL and DAL

Question

Solution setup:

• DAL (class library)
• BLL (class library)
• Common (class library (some common functionality - enums, logging, exceptions,...))

Answer 1

In my opinion you should have another Layer (seperate dll). Like "domain", where would you keep all entities like Customer. Then simply include in all higher levels(DAL, BLL, UI and others) in hierarchy this assembly.

Sample architecture can look like this:

(Database) <-> DAL <-> BL <-> UI

and on all levels you will have access to "domain" layer. DAL should return List not a DataTable. On some stage your development process you may want to use in DAL some OMR like NHibernate with would also return a List, probably.