Question

I have been searching for an answer to this question for days and it is driving me insane. Currently I am working on a project using ASP.NET MVC 3 and am trying to utilize a ViewModel per controller approach as has been suggested by so many articles and tutorials I have checked out. To better illistrate what I am asking I will outline below:

Lets say I have a pretty simple and straight forward model. Users, Customers, Addresses, Phone Numbers, Orders, Products, Categories, etc… When a user registers for a new account on my site I would like to:
1) create an account for them (this is just an account id, customer type)
2) Add their customer demographic data to Customers
3) Add N-addresses and address types
4) Add N-phone numbers with type as well.

As far as I have got is deciding that I need a RegisterCustomerForRegistrationControllerViewModel. My predicament is what does this model look like? I am trying to be as DRY as possible yet when implementing this pattern I seem to repeat myself at each turn. At what level do I put DataAnnotations for validation? So do I simply new up a new Customer() even if I only want to use one property from the class in a given ViewModel?

I’m not even confident at this point that this is a correct assumption. There seems to be so much opinion on the topic yet so few concrete examples of implementation. I am hoping someone can point me in the right direction and maybe present some code snippets along the way… I hope this is all clear enough and if not please feel free to ask follow up questions.

Again, Thanks in advance!

Answer 1

Repeating simple properties across two distinct layers of an application is not a violation of DRY. Its just good design.

DataAnnotations go on ViewModels.

ViewModel will look something like

public class RegisterCustomerViewModel
{
    [Required]
    public string Name { get; set; }
    public List<AddressViewModels> Addresses { get; set; }
    public List<PhoneNumberViewModel> PhoneNumbers { get; set; |

}