isual Studio supports transformations for web.config files that allow you to to change any details of your configuration during the deployment process, depending on your build configuration. This comes in handy to e.g. change application settings or connection strings for a release build, because typically those values will be different from the ones you are using during development or for test runs. One limitation of this feature is that it's only available for web.config files and cannot be applied to the configurations of client applications. Luckily, a nice solution to this exists.