I'm struggling to mesh two best practices together:

1. Using DataAnnotations + ModelBinding for validation in ASP.NET MVC 2
2. Using DTOs instead of domain entities when passing data via the ViewModel

If I want to pass over DTOs instead of domain entities, then leveraging DataAnnotations + ModelBinding for validation would require me to specify validation attributes on my DTO classes. This results in a lot of duplicated work since multiple DTOs may hold overlapping fields with the same validation restrictions. This means that any time I change a validation rule in my domain, I have to go find all DTOs that correspond with that value and update their validation attributes.