Una de las mejores prácticas en el desarrollo de .NET es el empleo de los diferentes blocks de la Enterprise Library (que por cierto son open source), de los cuales el más famoso sin duda es el Data Application Block. Recientemente se liberó la versión 3. Lo más sobresaliente:

• Validation Application Block. Allows you to centrally define validation rules using configuration or attributes, and easily validate data from anywhere in your application, including deep integration with Windows Forms, ASP.NET and WCF.
• Policy Injection Application Block. Provides an approach for separating cross-cutting concerns from business logic using declarative policies that are attached at runtime to methods on your objects. The block includes handlers that can call other Enterprise Library application blocks from policies, implementing functionality such as validation, authorization, exception handling, logging and caching.
• Application Block Software Factory. Dramatically simplifies the process of building application blocks and providers through the magic of guidance automation.
• Visual Studio-integrated Configuration Editor. Edit Enterprise Library configuration files directly within Visual Studio.
• Environmental Overrides. Use the configuration tool to specify configuration settings that are common or different across multiple deployment environments, and merge this information into configuration files to be deployed with your applications.
• WCF Integration. Easily integrate the Logging, Exception Handling and Validation Application Blocks into service interfaces built using Windows Communication Foundation.
• Pre-compiled, strong-named binaries. No need to compile and strong name the code unless you want to manage and evolve the code yourself.

Sitio de la descarga.

Sitio en MSDN

Sitio en Codeplex (código y comunidad de desarrollo).