Avalonia/build/EmbedXaml.props

<Project DefaultTargets="Build" 
  xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
  <ItemGroup>
     <Compile Update="**\*.xaml.cs">
      <DependentUpon>%(Filename)</DependentUpon>
    </Compile>
    <EmbeddedResource Include="**\*.xaml">
      <SubType>Designer</SubType>
    </EmbeddedResource>
  </ItemGroup>
</Project>