Overridden to validate that the Content property is a UIElement and to store a reference for easy access. The VisualBrush of the view finder display panel is also updated when the content changes.
Target Platforms: Windows 11, Windows 10, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2