https://learn.microsoft.com/zh-tw/uwp/api/windows.ui.xaml.input.gettingfocuseventargs?view=winrt-28000
GettingFocusEventArgs Class (Windows.UI.Xaml.Input) - Windows apps | Microsoft Learn
Provides data for the FocusManager.GettingFocus and UIElement.GettingFocus events.
classwindowsuixamlinput