Question

I’ve seen somewhere how to do this before on a blog but I forgot where or how. Lets say I have a domain in a class library. I’d like to data annotate the properties of this domain as my viewmodel in the web project.

How do I accomplish this?

For example. This domain is in my class library:

public class Person {
   public int Id {get; set;}
   public string FirstName {get; set;}
}

In my web project, there is this:

//Do i need to set some attribute here?
public class CreatePersonViewModel{

   [Required()]
   [DisplayName("First Name")]
   public string FirstName {get; set;}
}

This code can be mapped to Person without a tool. Probably partial or something.

Answer 1

The whole idea of using a view model is to decouple it from your domain model and to have something which is adapted to the needs of the view. The view model should be declared in the web project and contain all the necessary properties and formatting attributes that this particular view might require. The domain model shouldn’t be polluted with any view specific data annotations. So if your model looks like this:

public class Person {
   public int Id { get; set; }
   public string FirstName { get; set; }
}

You could have the following view model:

public class CreatePersonViewModel {
   [Required]
   [DisplayName("First Name")]
   public string FirstName { get; set; }
}

and then have the controller fetch the model from some repository, map it to the view model (AutoMapper can help you here) and pass the view model to the view.