This project provides common validation attributes (full list on the project website) which extend the built-in ASP.NET DataAnnotations (Required, Range, RegularExpression and StringLength). The core library provides server-side validation attributes that can be used in any .NET 4.0 project (no MVC dependency). There is also an easily pluggable client-side validation library which can be used in ASP.NET MVC 3 projects using unobtrusive jquery validation (only MVC3 included javascript files are required). All validation attributes are covered with unit tests and also have a dedicated controller in the included sample website (click Demos to see a demonstration of each validation attribute). Please see the project website for details: http://dataannotationsextensions.org/