As List & Label itself is a non-visual component, it can be used in WPF applications as well as in WinForms applications. The Designer itself is no WPF window, however this does not affect its functionality. The WPF Viewer can be used for displaying preview files and is a replacement for the WinForms PreviewControl.
Please note that the WPF viewer relies on the existence of the XPS Document Writer printer driver on the target system. If the driver is not available, documents cannot be displayed.