Nullability of reference types in type of 'event PropertyChangedEventHandler GhisTabHeaderControl.PropertyChanged' doesn't match implicitly implemented member 'event PropertyChangedEventHandler? INotifyPropertyChanged.PropertyChanged'.

Nullability of reference types in type of parameter 'parameter' of 'bool RelayCommand.CanExecute(object parameter)' doesn't match implicitly implemented member 'bool ICommand.CanExecute(object? parameter)' (possibly because of nullability attributes).

Nullability of reference types in type of parameter 'parameter' of 'void RelayCommand.Execute(object parameter)' doesn't match implicitly implemented member 'void ICommand.Execute(object? parameter)' (possibly because of nullability attributes).

Non-nullable field '_child' must contain a non-null value when exiting constructor. Consider declaring the field as nullable.

Non-nullable field '_parentControl' must contain a non-null value when exiting constructor. Consider declaring the field as nullable.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

Dereference of a possibly null reference.

Dereference of a possibly null reference.