patterns & practices Enterprise Library 5.0 is now available on MSDN.   Microsoft Enterprise Library (EntLib) is a collection of application blocks (reusable software components) designed to address common cross-cutting concerns (data access, exception handling, logging, validation, ...etc.)  EntLib provides source code, test cases, and docs that you can use "as is" or extend as you see fit.  The goal of EntLib is to codify Microsoft recommended and proven practices for .NET application development.

What's New in 5.0
Enterprise Library 5.0 brings the following to the table:

• Major architectural refactoring that provides improved testability and maintainability through full support of the dependency injection style of development
• Dependency injection container independence (Unity ships with Enterprise Library, but you can replace Unity with a container of your choice)
• Programmatic configuration support, including a fluent configuration interface and an XSD schema to enable IntelliSense
• Redesign of the configuration tool to provide: a more usable and intuitive look and feel, extensibility improvements through meta-data driven configuration visualizations that replace the requirement to write design time code, a wizard framework that can help to simplify complex configuration tasks
• Data accessors for more intuitive processing of data query results
• Asynchronous data access support
• Honoring validation attributes between Validation Application Block attributes and DataAnnotations
• Integration with Windows Presentation Foundation (WPF) validation mechanisms
• Support for complex configuration scenarios, including additive merge from multiple configuration sources and hierarchical merge
• Optimized cache scavenging
• Better performance when logging
• Support for the .NET 4.0 Framework and integration with Microsoft Visual Studio 2010
• Improvements to Unity: Streamlined configuration schema, a simplified API for static factories and interception, the capability to add interface implementation through interception, additional types of lifetime manager, deferred resolution (automatic factories), a reduction of the number of assemblies

Key Links

• Enterprise Library 5.0 Home (MSDN)
• Download Enterprise Library 5.0 (Microsoft.com)
• Release Notes (CodePlex)
• Documentation (CodePlex)
• Community Forum (CodePlex)
• Developer's Guide (CodePlex)