Question

I have a ASP.NET MVC solution with three projects:

1. SquarkMVC
2. SquarkBLL
3. SquarkDAL

The SquarkDAL layer has Linq2SQL classes for each object in the DB. BLL references the DAL in order to conduct business logic on the DB.

My question is this… without having to reference the DAL in the MVC layer, how should I model the entities of the DB in the MVC layer? For instance, if I have a sign up form in the MVC layer, what is the best way to take that information, pass it to the Business Layer which then passes it on to the Data Layer? I don’t want the MVC layer to know anything about the DAL.

I’ve found this answer on another post… is it generally agreed that the best way to overcome this is to create a transfer object in order to pass the information from the presentation layer, to the business layer, which will then convert the information into the entity classes used by the DAL?

Hope this makes sense.

Answer 1

Using objects is a common way to do this. Usually DTOs (Data Transfer Objects) are “dumb” POCOs having a set of properties, and acts like a “struct”, but, if you put on them validation and more logic (view logic) you have a view model and you can use them to work with the controller. This one should use the model (of the Business Layer).

More, Business Layer should never having a reference to the DAL, because your business model should be independent by the storage.
Instead, the data access layer should reference the model, and choose the right way for persistence. You can achieve it with the Repository pattern.

Anyway there are a lot of books about domain driven design.