WPF UserControl cannot find XAML resource in referencing project

Question

In my WPF project i keep a user control in a separate library project. The user control accesses resources in a separate XAML file, like this:

Answer 1

In my case I had the ResourceDictionary and the UserControl on the same Library, but separate from the main application. What worked for me was specifying the name of the assembly in the format Adam suggested in the comment AND I had to change the ResourceDictionary in the project from Embedded Resource to Page. I didn't try using the pack:// format, but I assume it would work too.