Validation in a Domain Driven Design

public interface IValidator<T>
{
    bool IsValid(T entity);
    IEnumerable<string> BrokenRules(T entity);
}

public class OrderPersistenceValidator : IValidator<Order>
{
    public bool IsValid(Order entity)
    {
        return BrokenRules(entity).Count() > 0;
    }

    public IEnumerable<string> BrokenRules(Order entity)
    {
        if (entity.Id < 0)
            yield return "Id cannot be less than 0.";

        if (string.IsNullOrEmpty(entity.Customer))
            yield return "Must include a customer.";

        yield break;
    }
}

person.Address = "123 my street";
 person.City = "Houston";
 person.State = "TX";
 person.Zip = 12345;

person.ChangeAddress(.......);

bool IsVerifiedBy(TEntity candidate)

IEnumerable<string> BrokenRules(TEntity canditate)

bool IsVerifiedBy(TEntity candidate)
{
  return BrokenRules(candidate).IsEmpty();
}

IEnumerable<string> BrokenRules(TEntity candidate)
{
  if (someComplexCondition)
      yield return "Message describing cleary what is wrong...";
  if (someOtherCondition)
      yield return
   string.Format("The amount should not be {0} when the state is {1}",
        amount, state);
}