c# - Attribute on Interface members does not work

Question

In my application several models need Password properties (eg, Registration and ChangePassword models). The Password property has attribute like DataType and Required. Therefore to ensure of re-usability an consistency, I created :

interface IPasswordContainer{
    [Required(ErrorMessage = "Please specify your password")]
    [DataType(DataType.Password)]
    string Password { get; set; }
} 

And

class RegistrationModel : IPasswordContainer {
    public string Password { get; set; }
}

Unfortunately, the attributes does not work.

Then I tried changing the interface to a class:

public class PasswordContainer {
    [Required(ErrorMessage = "Please specify your password")]
    [DataType(DataType.Password)]
    public virtual string Password { get; set; }
}

And

public class RegistrationModel : PasswordContainer {
    public override string Password { get; set; }
}

Now it is working. Why it is so?

Why the attributes are working when inherited from class but not working when inherited from interface?

Answer 1

Attributes on interface properties doesn't get inherited to the class, you may make your interface an Abstract Class.

Found an answer from Microsoft:

The product team does not want to implement this feature, for two main reasons:

• Consistency with DataAnnotations.Validator
• Consistency with validation behavior in ASP.Net MVC
• tricky scenario: a class implements two interfaces that have the same property, but with conflicting attributes on them. Which attribute would take precedence?