There is a great open source project on codeplex: .NET validation framework. This project apply reusable and customizable validation rules to properties, methods, and parameters in your business objects. Works with WPF , ASP.Net , Windows Forms , ASP.Net MVC and web services . (This library is written in C# but can be consumed by any .net assembly) Requires: .net Runtime 3.0. I really recommend to use this framework it is very strong and easy to use. Want to read more? here is the link to codeplex...