An example IPreviewHandler implementation using .NET Windows Forms.
Preview handlers are called when an item is selected to show a lightweight, rich, read-only preview of the file's contents in the view's reading pane. This is done without launching the file's associated application.
https://docs.microsoft.com/en-us/windows/win32/shell/preview-handlers
https://www.brad-smith.info/blog/archives/79
https://www.brad-smith.info/blog/archives/183
https://github.com/GeeLaw/PreviewHost