This post is a quick tip on how to manage multiple app.config or web.config files in Visual Studio. Consider the typical development environment for a project where we have development / QA / Production. Each environment has its own database and other settings. We need a way to be able to run the app but use the pertinent config settings. This technique allows for us to create config files for each environment but still have a clean way to use the respective config.
In short it comes down to leveraging pre-compile events and the configuration manager within Visual Studio.
Check it out as it is a real nice time saver.
http://www.hanselman.com/blog/CommentView.aspx?guid=93bfa4b3-44cd-4681-b70e-f4a2b0386466