I saw a preview of an interesting new feature in Enterprise Library (EntLib) 3.0 this morning. When released this will allow EntLib users to create delta configurations. In practice, the user first creates a base configuration and then adds new top-level configuration sections called for example Dev, Test, or Production. Then, for each of the nodes in the main configuration, there is a subnode (Dev) which allows you to override the property definitions in the base configuration and specialize them for the different environments. Then you can select the top level delta node and export the XML combining the base configuration with the delta overrides. There is also a command line version that allows you to integrate this into your build process. Good Stuff!