Does RelayCommand and ObservableProperty have to be in same class in order for "CanExecute" to check property value?

[robinne]

WPF "CanExecute" has always worked because it is constantly polling the "CanExecute" to know if it can run. I know that this has change with MVVM Toolkit and any property that can affect a command must have "NotifyCanExeuteChangedFor" attribute to specifically identify commands to re-run logic for.
What I cannot figure out is, how can I architect my program with many classes (view models) where the observable property is not going to reside in the same class as the relay command.

// a property not in same class as XXXXCommand, fails. You cannot reference it
[ObservableProperty]
[NotifyCanExecuteChangedFor(nameof(XXXXCommand))]
public string _firstName;

I've tried to reference with the class name that the Command resides in, but the project fails with: The target(s) of [NotifyCanExecuteChangedFor] must be an accessible IRelayCommand property, but "ChangePersonNameCommand" has no matches in type WpfApp1.ViewModel.PersonViewModel

Thanks