What is DesktopWindowXamlSource?
DesktopWindowXamlSource is the main class in the UWP XAML hosting API that enables non-UWP desktop applications to host any control that derives from Windows. In other words, a Windows API allows an app to host XAML controls within a desktop (Win32) window. If you see an empty window as the issue been addressed, then it's likely the API is being misused or there is an error in the implementation.