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

I thought it was worth posting this just in case anyone else is struggling with the same problem, as I've spent over two hours fighting with syntax, etc. only to find that the solution was dead simple, but not that apparent: When referencing a packed resource from another control library, it seems to work fine at design time, and even compiles without error, but fails at runtime with the 'Set property 'System.Windows.ResourceDictionary.Source' threw an exception' error. It turns out that simply referencing the resource assembly from your control library is not enough, you ALSO need to add a REFERENCE to the assembly containing the resource dictionary in you main application assembly, else it seems it does not get compiled into the application. (i.e. Startup Application (the one with app.xaml) -> Add Reference -> select assembly with referenced resource file/s).

Hope this helps!