Build a named capture group (X being the pattern you want to capture):
(?'name'X)
(?X)
(?PX)
Reference a named capture group:
${name}
\{name}
g\{name}
Python and Java don't allow multiple groups to use the same name.
This app sample is available on my GitHub below:
https://github.com/Daniel-Krzyczkowski/XamarinAndroid/tree/master/AndroidPictureOrientation/PictureOrientationApp
Xamarin Mobile component documentation is available below:
https://components.xamarin.com/view/xamarin.mobile