the relevant quote is:    > A ResourceDictionary defined inside of a [UserControl](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.usercontrol) carries a penalty. The platform creates a copy of such a ResourceDictionary for every instance of the UserControl. If you have a UserControl that is used a lot, then move the ResourceDictionary out of the UserControl and put it at the page level.  