WM8.1

XAML

Button drehen

<Button x:Name="nextButton"
        Click="AcceptHandler" 
        RenderTransformOrigin="0.5,0.5" 
        Style="{StaticResource NavigationBackButtonNormalStyle}">
               
   <UIElement.RenderTransform>
      <RotateTransform CenterX="0.5" CenterY="0.5" Angle="180" />
   </UIElement.RenderTransform>
</Button>