Make `SelectionModelChildrenRequestedEventArgs.Children` an observable, so that the we can react to the children collection object changing, as well as the children inside the collection changing.
Upstream issue: https://github.com/microsoft/microsoft-ui-xaml/issues/2404
Added a new `IsEnabledCore` property to `InputElement` which is overridden in `Button` and `MenuItem` to override the `IsEffectivelyEnabled` state with the enabled state of the command.
Also add data validation of the `Command` property to `MenuItem` to make it behave the same as `Button` when `Command` is bound to a non-existent property.
Fixes#2501
I now understand how WPF's `IsEnabledCore` works, and it's not like this. Rename `IsEnabledCore` to `IsEffectivelyEnabled` so that we can add a new `IsEnabledCore` property which works like WPF's.
This also aligns with the existing `IsEffectivelyVisible` property.
Emmanuel Hansen
Steven Kirk
Giuseppe Lippolis
robloo
Max Katz
abdesol
ReeJK
Nikita Tsukanov
Steven Kirk
Andrey Kunchev
Jeremy Koritzinsky