"Add as Link" for folders in Visual Studio projects

As this blogpost stated, it is possible.

<ItemGroup>
    <Compile Include="any_abs_or_rel_path\**\*.*">
        <Link>%(RecursiveDir)%(FileName)%(Extension)</Link>
    </Compile>
</ItemGroup>

But be aware, the files will not be copied.

In VS2012 and later, you can drag a folder to another project with alt key pressed. It's just the same as adding each file as link manually but faster.

upd: Consider using Shared Projects if you are using VS2013 update 2 (with Shared Project Reference Manager) or VS2015.