The transparency effect is called “Acrylic” and is part of Microsoft’s new design language.
When and how to use it is explained on MSDN.
In a nutshell, you simply need to apply an AcrylicBrush
on whatever surface you want to make transparent. The BackgroundSource
allows you to tell whether you want the transparency to be relative to your app (you’ll see your background controls) or to the desktop (you’ll see the wallpaper/other windows).
Note that it’s a bit early to build applications based on this API, as it’s only available on Insider builds of Windows with the preview SDK, and is subject to change. Though if you want your app to be ready for launch, it’s a good thing to start playing with it.
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solved How to make transparent WUA app just like new windows 10 calculator is on hold? [closed]