Recursive include of c# files in a project

recursive_include.csproj

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>netcoreapp2.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <Compile Include="..\SomeOtherProject\SomeFolder\*.cs">
      <Link>%(RecursiveDir)%(FileName)%(Extension)</Link>
    </Compile>
  </ItemGroup>
</Project>

SomeWebProject.csproj

<Project Sdk="Microsoft.NET.Sdk.Web">
 <PropertyGroup>
   <!-- ...
    based on https://stackoverflow.com/questions/7643615/how-can-i-get-msbuild-to-copy-all-files-marked-as-content-to-a-folder-preservin
    -->
   <WWWRoot>$(ProjectDir)wwwroot</WWWRoot>
 </PropertyGroup>
 <ItemGroup>
   <!-- Specify a file collection WWWRootFiles: -->
   <WWWRootFiles Include="..\wwwroot\**\*.*"></WWWRootFiles>
  </ItemGroup>
  <Target Name="CopyContentFiles" AfterTargets="Build">
    <!-- Copy files into the relative folder: -->
    <Copy SourceFiles="@(WWWRootFiles)"
          DestinationFiles="@(WWWRootFiles->'$(WWWRoot)\%(RelativeDir)\%(Filename)%(Extension)')" />
  </Target>
</Project>

See https://blog.samstephens.co.nz/2010/10/18/msbuild-including-extra-files-multiple-builds/