HandyControl/src/Shared/HandyControlDemo_Shared/UserControl/Controls/RelativePanelDemoCtl.xaml

<UserControl x:Class="HandyControlDemo.UserControl.RelativePanelDemoCtl"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:userControl="clr-namespace:HandyControlDemo.UserControl">
    <userControl:UnderConstruction/>
</UserControl>