https://github.com/MicrosoftArchive/enterprise-library
Summary: The Policy Injection Application Block can be used to change the behavior of your custom objects, and almost any other .NET class in the Aspect-Oriented Programming (AOP) fashion, in order to better manage crosscutting concerns for these objects. It changes the behavior of your objects by injecting custom behaviors at run time. Policy injection is now implemented through the Unity interception mechanism, which supports transparent proxy interception, interface interception and virtual method interception. The Policy Injection Application Block contains handlers to add capabilities from other Enterprise Library blocks (such as validation, logging, and exception handling) to objects in your applications.
Microsoft patterns & practices http://microsoft.com/practices