Including files in Visual Studio project files, where it may be in one of a few places

projectFile.xml

<!-- Fragment showing conditions for both location and target platform -->

  <PropertyGroup>
    <InternalPath>..\..\Installers\Binaries</InternalPath>
    <ExternalPath>..\..\..\..\..\Installers\Binaries</ExternalPath>
  </PropertyGroup>
  <ItemGroup>
    <WixLibrary Include="Template" Condition=" '$(Platform)' == 'x86' ">
      <HintPath Condition="Exists('$(InternalPath)')">$(InternalPath)\x86\Template.wixlib</HintPath>
      <HintPath Condition="Exists('$(ExternalPath)')">$(ExternalPath)\x86\Template.wixlib</HintPath>
      <Name>Template</Name>
    </WixLibrary>
    <WixLibrary Include="Template" Condition=" '$(Platform)' == 'x64' ">
        <HintPath Condition="Exists('$(InternalPath)')">$(InternalPath)\x64\Template.wixlib</HintPath>
        <HintPath Condition="Exists('$(ExternalPath)')">$(ExternalPath)\x64\Template.wixlib</HintPath>
      <Name>Template</Name>
    </WixLibrary>
  </ItemGroup>

projectFile2.xml

<PropertyGroup>
    <SharedPathDeep>..\..\..\..\Shared Code</SharedPathDeep>
    <SharedPathShallow>..\..\..\Shared Code</SharedPathShallow>

    <SharedCodePath Condition="Exists('$(SharedPathDeep)')">$(SharedPathDeep)</SharedCodePath>
    <SharedCodePath Condition="Exists('$(SharedPathShallow)')">$(SharedPathShallow)</SharedCodePath>
</PropertyGroup>

  <ItemGroup>
    <None Include="$(SharedCodePath)\MyKey.snk">
      <Link>MyKey.snk</Link>
    </None>
  </ItemGroup>