ASP.Net MVC and N-Tier

Question

Greetings,

Apologies in advance that I have not researched this toughly enough to answer the question myself, but I imagine it would take me some time and I would rather know now before I invest more time in learning it. I couldn't find anything in my initial research..

Why use ASP.Net MVC if your already using a multi-tier architecture (Data Layer, Logic Layer, Presentation Layer)? Other than the fact the controller has more power than the logic layer.

Am I right in thinking I can use nHibernate and all my data access classes, entities, and mappings in the Model part of the MVC?

When using controllers, is it best to separate a lot of the logic into a separate class so I can call it from multiple controllers? Or can I call them from the controllers themselves, considering the fact that I would not want all of them to be Actions, just normal methods.

Thanks

Answer 1

MVC is not to replace N-Tier, it is a way to organize the presentation layer.

I would not say that the controller is more powerful than the logic layer. Instead, the controller (as a part of the presentation layer) should still call the logic layer.

Controllers should only prepare data for views and handle actions from views. You should still use your BLL.

Answer 2

Yes, NHibernate entities can (and they should be) be passed to the views.

This will you get you into some trouble. You should use flattened, null-safe DTOs a.k.a. view models.

Answer 3

Damien, you might want to read these 2 posts:

The Fat Controller

An Architectural View of the ASP.NET MVC Framework

Answer 4

N-tier is an archtitectual pattern, to enable reuse, seperaation of concerns and scalability of the key areas of your application. The non UI layers (Business, Data, Facade etc.) should be unit tested and UI agnostic.

The UI layer is just one of these layers weather it be Silverlight, ASP.NET MVC, web forms etc.

MVC, like MVP is a design pattern that enables better testability of the UI Layer. ASP.Net MVC is an out of the box framework that supports and enforces this pattern. The pattern was arround an in use long before this framework.

But this is simply a UI layer choice, There should be no interaction with databases, services etc in the controllers, they control the state of the view using the model, Should not control the business logic, peresistence, transactions etc.

Answer 5

To answer your question on why use if you are already going multi-tier is that it makes for more organized and search-engine friendly URL's. Also, it is more of a standard pattern than the other patterns tend to be in ASP.Net. That makes it more developer friendly for those that are already using MVC on other platforms.