In well designed enterprise apps, it is often the case that your application will run in multiple environments, and against different databases (Development, Test, and Production). This can lead to issues when it comes to storing connections strings.

Using Visual Studio 2003, there was an option to override your application config file as described by Stephen Chu’s post. I couldn’t get this setting to work in Visual Studio 2005, and I assume it is deprecated as MSDN the seems to have very little documentation about the setting One way I managed to find around it is to add something similar to the following in your .proj file (.csproj, .vbproj, …)

</ItemGroup>
  <Import Project=“$(MSBuildBinPath)\Microsoft.VisualBasic.targets“ />
  <!– To modify your build process, add your task inside one of the targets below and uncomment it.
       Other similar extension points exist, see Microsoft.Common.targets.
  –>

  <Target Name=“BeforeBuild“>
    <CreateProperty Value=“app.debug.config“ Condition=“ ‘$(Configuration)|$(Platform)’ == ‘Dev|AnyCPU’ “>
      <Output TaskParameter=“Value“ PropertyName=“AppConfig“ />
    </CreateProperty>

    <CreateProperty Value=“app.test.config“ Condition=“‘$(AppConfig)’==” and ‘$(Configuration)|$(Platform)’ == ‘Test|AnyCPU’ “>
      <Output TaskParameter=“Value“ PropertyName=“AppConfig“ />
    </CreateProperty>
    <CreateProperty Value=“app.prod.config“ Condition=“‘$(AppConfig)’==” and ‘$(Configuration)|$(Platform)’ == ‘Prod|AnyCPU’ “>
      <Output TaskParameter=“Value“ PropertyName=“AppConfig“ />
    </CreateProperty>
    <CreateProperty Value=“app.config“ Condition=“‘$(AppConfig)’==”“>
      <Output TaskParameter=“Value“ PropertyName=“AppConfig“ />
    </CreateProperty>
  </Target>

  <!–<Target Name=”AfterBuild”>
  </Target>–>
</Project>

This basically sets the $(AppConfig) variable to something sane (depending on your chosen configuration). When the _CopyAppConfigFile target (see Microsoft.Common.targets) runs it copies this file to the output directory.

An alternative would be to write a new task to replace _CopyAppConfigFile and import it with the line