Argument of type '(ThemeInfo? theme, string subdir)' cannot be used for parameter 'item' of type '(ThemeInfo, string)' in 'void List<(ThemeInfo, string)>.Add((ThemeInfo, string) item)' due to differences in the nullability of reference types.

Converting null literal or possible null value to non-nullable type.

Cannot convert null literal to non-nullable reference type.

Cannot convert null literal to non-nullable reference type.

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

Nullability of type of parameter 'obj' doesn't match overridden member (possibly because of nullability attributes).

'Monitor' overrides Object.Equals(object o) but does not override Object.GetHashCode()

Nullability of reference types in type of 'event EventHandler RelayCommand.CanExecuteChanged' doesn't match implicitly implemented member 'event EventHandler? ICommand.CanExecuteChanged'.

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).

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).