Question

I’ve been fiddling with some ASP.NET MVC3 solution structures and I have settled on a design that is made up of the following projects:

MyApp.Web -  MVC3 Web Layer
MyApp.Data - Repositories and infrastructure for managing data
MyApp.Domain - POCO Entities
MyApp.Service - Service layer through with I manipulate the model
MyApp.Test - doh

Where would you put your custom validation attribute classes? As far as I’m concerned they should go in the Domain project because they are specific to the entity classes that live there, but then I would need to reference a number of dlls such as System.Web.MVC and I would have liked to have kept references in that project to a bare minimum. Thoughts?

Update:

I removed all attributes from my Domain project and created view models to wrap them in the Web project.
Placed all my custom validation classes in a folder in the web project. Thanks guys

Answer 1

You do not need to reference the web dlls. Only System.ComponentModel.DataAnnotations

Put the validation attributes where they are use.d

Update

Why not? Almost every example I’ve seen uses POCOs in views. What’s the alternative? Creating some kind of wrapper classes for my POCOs?

Because of:

Security

Let’s say that you got a User POCO with an IsAdmin field. By using the POCO, the ModelBinder in MVC will set that property if it’s POSTed by a “hacker” who therefore gain admin access.

Isolation

Using the POCO in your view makes your View indirectly dependent of your database. Sure, POCOs are supposed to remove that dependency. But in reality they seldom do.

Customization

You do seldom show all values in a view as they are stored in the db.

The code to adapt a model should not be in the view, but in the viewmodel. Use as little logic as possible in your views.