"XAML provides an easy way to set values of properties—type converters and the extended property syntax allow for flexible setting of values. However, some things cannot be expressed as a simple value, such as setting a property to the value of some static property."

这个相对比较简单，知道就行，Code Snip如下：

    <StackPanel>
        <Ellipse Stroke="Black" Height="50" Fill="{x:Static SystemColors.DesktopBrush}"/>
        <Rectangle Stroke="Black" Height="50" Fill="{x:Static SystemColors.ActiveCaptionBrush}"/>
    </StackPanel>

请对比：WPF整理-使用用户选择主题的颜色和字体 ，区别两者的不同点。