Adding Validation Attributes With an Entity Framework Data Model

Question

Preface Feb 2015 If you are still using Entity Framework EDMX, please do yourself a favor and checkout using Entity Framework Code First instead. The differ

Answer 1

I know this has been marked answered but I want to clear some stuffs up.

@SteveCav said: "This member is defined more than once". I had the same exact same error. Spent hours trying to figure out.

To finally correct it, you have to create a separate file class in the same Assembly(I think this is already mentioned here). But what I want to stress is that this class should be nested with a partial class representing the Inner Class.

And then you decorate that inner class with the Annotation class. Like this:

//ContactMap.cs - Present in the same namespace as Contact.cs
[System.ComponentModel.DataAnnotations.MetadataType(typeof(ContactMap))]
partial class Contact // Present in the ContactMap class. This represent the Inner Class
{
}

//ContactMap.cs - This represent the outer class

using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
public class ContactMetadata
{
    [Required(ErrorMessage = "Name is required.")]
    [StringLength(5)]  
    public string ContactName;
}

Hope this is clearer or more understandable.