System Fonts in WPF

The code snippet below shows how to use System Fonts and System Colors in WPF.
Button button1 = new Button();
button1.Content = "SystemFonts";
button1.Background = SystemColors.ControlDarkDarkBrush;
button1.FontSize = SystemFonts.IconFontSize;
button1.FontWeight = SystemFonts.MessageFontWeight;
button1.FontFamily = SystemFonts.CaptionFontFamily;