Question

In my solution I have an ASP.NET MVC3 project, and a WCF project that works with a database. I will use AutoMapper to map objects.

My question is: can I use DataAnnotations with my viewmodel classes, and map them to objects received from the WCF service project?

Like

public class User
{
    [Required,MaxLength(30)]
    public string UserName { get; set; }

    [Required]
    public string Email { get; set; }
}

Answer 1

I use them for two things:

• Entity Framework mappings to tell Entity Framework how to generate a column (although I usually use the fluent API for this)
• Input validation, so this is where your ViewModel comes in. You can annotate it with the dataannotations, and use jquery.validate and MVC’s ModelState.IsValid to verify that all requirements were met.

When everything is alright you can map the ViewModel to a POCO/entity without annotations.