Differences between WPF Custom Control Library and plain Class Library?

Question

I posted a question a few months ago about sharing resource dictionaries across assemblies. It turns out you can do that using the Component Resource Key markup extension. A

Answer 1

Another difference is in the .csproj File:

In class Library the Tag is missing:

{60dc8134-eba5-43b8-bcc9-bb4bc16c2548};{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}

After adding it to the first PropertyGroup, the add menu of the project shows now the typical WPF files.