I spent a little bit of time trying to figure this out, to be honest – it’s available in quite a few locations on google, but I thought I’d add it here as well. The basic problem is, you have your template / theme etc for your control in a separate project;
MyThemes : DateTimeThemes/Theme1.xaml etc
and you want to use this as a resource for your control, how?
You add into your Resources element (be it in Window.Resources or UserControl.Resources), like so:
<ResourceDictionary Source="/MyThemes;component/Themes/Theme1.xaml" />
What’s important here is that the word ‘component’ is as spelt, you don’t replace it with anything (like ‘MyComponent’ for example), just leave it as is.
is the name of the dll, which isn’t necessarily the name of the project – (though that would only change if you’ve changed those properties).