<?xml version="1.0" encoding="utf-8"?>
<Project ToolsVersion="4.0" DefaultTargets="Demo" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">

<UsingTask TaskName="TransformXml"
      AssemblyFile="$(MSBuildExtensionsPath)MicrosoftVisualStudiov12.0WebMicrosoft.Web.Publishing.Tasks.dll" />

<Target Name="AfterBuild">
  <TransformXml Source="ConfigApp.config"
                Transform="ConfigApp.$(Configuration).config"
                Destination="$(OutputPath)$(AssemblyName).$(OutputType).config" />
</Target>