Question

I’ve got my DL project abstraction (seperate assmebly for my DL) I’ve got a BL (seperate assembly)..where it’s got intermediate methods that are calling some db layer methods. But some of those DL methods need to return a type that’s in my BL…that would force a problem, a circular reference. How are you handling this in terms of patterns?

so for instance if I have a hypothetical MyProject.DL has the following method in the Car class:

internal List<Car> GetCars(Dealer dealer)
{
   // logic

}

and MyProject.BL needs to call that DL method:

public List<Car> GetCars(Dealer dealer)
{
     MyProject.DL.GetCars(dealer);
}

Answer 1

I’d personally separate it out so I had three assemblies:

• My.Project.DL
• My.Project.BL
• My.Project.Types

I’d put any shared types in the My.Project.Types library, as long as they contained no logic of their own and were only populated/manipulated by methods in the DL and BL libraries.

For example:

In My.Project.Types

namespace My.Project
{
    public sealed class Car()
    {
        public int CarId { get; set; }
        public string CarName { get; set; }
    }
}

Now both My.Project.DL and My.Project.BL would reference the My.Project.Types assembly and thus obtain the Car type from there. Note that I haven’t namespaced the Car class into a namespace called My.Project.Types because that namespace would be spurious and somewhat pointless, instead I’ve left them in My.Project which makes much more sense.