If you are going to learn WPF, UWP, Xamarin, etc, I can't recommend strongly enough to learn the Data Binding used by these UI frameworks:
Data Binding Overview | Microsoft Docs[
^]. The key is to learn Data First programming - ie: work with the data, not controls.
Here is an example where the dev was focusing on working directly on the control to access the data rather than on the data itself through data binding which the solution uses:
How to check WPF datagrid checkbox is selected or not in all rows in button click event[
^]
Once you understand Data Binding, then learn MVVM.
Once you master these two design patterns, you have learned the core of all of these UI frameworks.