Along with with .Net version 4.0 came DataAnnotations which is a library for validating properties in classes. The library consists of validation-attributes, core classes and interfaces for validating properties. Using DataAnnotations to validate the UI is modern, elegant and is understood straight out of the box by Microsoft frameworks such as ASP.Net MVC and WPF, as long as the platform is .Net 4.0 or above. Now, wouldn’t it be nice if we could extend the usage of DataAnnotations and annotate the ......