How I do define and apply themes to my custom control that is hosted in an ElementHost.
VS created Generic.xaml in the Themes folder. If I renamed it to something else (like Blue.xaml), the entire control does not show up.
Another question is what theme xaml files should be set to in VS: Content, Page or Resource?
You should always have a Generic.xaml defined.
Copy it, and then change your Blue.xaml to define your “Blue” theme.
Build Action = Page
See as you’re hosting your WPF control in a Windows Forms Application with ElementHost, then you might have difficulty in it seeing changes to the theme.
See:
http://www.actiprosoftware.com/community/thread/20266/how-to-get-themes-working-inside-an-elementho
Dynamic Application-level resources are not dynamic when hosted in ElementHost