Setting PopupBox.Opened via Style-EventSetter fails

[greuelpirat]

Bug explanation

the following style

<Style TargetType="materialDesign:PopupBox" BasedOn="{StaticResource MaterialDesignPopupBox}">
    <EventSetter Event="Opened" Handler="OnPopupBoxOpened" />
</Style>

fails because of strict type check:
https://github.com/dotnet/wpf/blob/01559f6a23310e1361adbc8916909088b7a45ce0/src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/EventSetter.cs#L115

because the type of PopupBox.OpenedEvent (as well as PopupBox.ClosedEvent) is EventHandler
it should be RoutedEventHandler

Version

4.7.1