ASP.NET 4 Unleashed

Performing Validation with the EntityBase Class

One complaint I’ve always had about ASP.NET Framework is that validation happens at the wrong place. When building ASP.NET pages, you write the vast majority of your validation code in the user interface layer instead of your business logic layer where your validation code properly belongs.

Performing validation in your user interface layer is bad for two main reasons. First, it means that if you switch user interfaces for your application, you must rewrite all your validation logic. For example, you might want to create a cool Silverlight interface for your application. In that case, you have to write all your validation logic again from scratch. Validation logic should be user interface-independent. ...