Managing complex Web.Config files between deployment environments

We split out all region specific settings into thier own config file. Under the root of the web app we create a config folder and place the region specific settings there. So whatever files are living under the root of config will get picked up.

our web.config looks something like:

.
.
.
<appSettings configSource="config\appSettings.config"/>
<nlog configSource="config\nlog.config"/>
<applicationSettings>
    <MyApp.UI.Properties.Settings configSource="config\Settings.APGUI.config"/>
    <MyApp.BusinessServices.Properties.Settings configSource="config\Settings.Business.config"/>
    <MyApp.Auditing.Properties.Settings configSource="config\Settings.Auditing.config"/>
</applicationSettings>
.
.
.

So if we are deploying to the release region the build tool will just have an action to replace the files in the root of config with the files from the appropriate region folder. The file structure looks something like:

ADDED: This is how the source control structure looks, the deployed app would just have the config dir with no sub folders or course

\Root
   web.config    
   \Config    
       appsettings.config    
       services.config    
       logging.config    
       \release    
          appsettings.config    
          services.config    
          logging.config    
       \debug
          appsettings.config    
          services.config    
          logging.config

It is pretty clean and supported by any automated build tool(copying/replacing files). The nice side effect is that developers can create different flavors and keep them under source control without affecting the “real” configs.