I have recently posted a supremely belated response to a similar SO topic:
https://stackoverflow.com/a/27546685/2798367
I will repeat it here for clarity:
This is somewhat late to the party, but I stumbled upon a nice way of implementing the web.transform
approach for app.config
files. (i.e. it makes use of the namespace http://schemas.microsoft.com/XML-Document-Transform
)
I think it is "nice" because it is a pure xml approach and doesn't require 3rd party software.
A parent / default App.config file is descended from, according to your various build configurations.
These descendants then only override what they need to.
In my opinion this is much more sophisticated and robust than having to maintain x
number of config files which get copied in their entirety, such as in other answers.
A walkthrough has been posted here: http://mitasoft.wordpress.com/2011/09/28/multipleappconfig/
Look, Mom - No explicit post-build events in my IDE!