Xamarin.Forms-Samples/Xamarin.Forms-Styles/Xamarin Styles/Xamarin_Styles/App.xaml

<?xml version="1.0" encoding="utf-8" ?>
<Application xmlns="http://xamarin.com/schemas/2014/forms"
					   xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
					   x:Class="Xamarin_Styles.App">
  <Application.Resources>
    <ResourceDictionary>
      <Style x:Key="AppButtonStyle"
             TargetType="Button">
        <Setter Property="Rotation" Value="25" />
      </Style>
    </ResourceDictionary>
  </Application.Resources>
</Application>