The "Silverlight Business Application" template bundled with VS2010 / Silverlight 4 uses DataAnnotations on method arguments in its domain service class, which are invoked automagically:

        public CreateUserStatus CreateUser(RegistrationData user,
        [Required(ErrorMessageResourceName = "ValidationErrorRequiredField", ErrorMessageResourceType = typeof(ValidationErrorResources))]
        [RegularExpression("^.*[^a-zA-Z0-9].*$", ErrorMessageResourceName = "ValidationErrorBadPasswordStrength", ErrorMessageResourceType = typeof(ValidationErrorResources))]
        [StringLength(50, MinimumLength = 7, ErrorMessageResourceName = "ValidationErrorBadPasswordLength", ErrorMessageResourceType = typeof(ValidationErrorResources))]
        string password)
    { /* do something */ }

If I need to implement this in my POCO class methods, how do I get the framework to invoke the validations OR how do I invoke the validation on all the arguments imperatively (using Validator or otherwise?).