Is it possible to load Window without showing it?

[lostmsu]

I'm on Windows, and I need my controls loaded in background, but only shown upon user request. Some of the controls are native.

This happens in a separate Window. Unfortunately, none of the controls neither the Window itself ever get Loaded event until I call Window.Show()

[maxkatz6]

No. Loaded event is well defined, and it can't be raised before window is actually showing.

If you need to cut down JIT time, making window load faster, look into ReadyToRun or AOT solutions.
If you need to run initialization code before window opened, you should move this code out of the window loaded event.