I've build a custom TextBox control which works properly in WPF. It makes use of DynamicResource bindings for all its brushes. In Noesis every interaction with the TextBox and probably every re-render logs the following error: [Error]: "[noesis] Freezable object cannot be made unmodifiable". This happens for the SelectionBrush, CaretBrush and Foreground properties. It does look like that at least the Foreground brush does get properly updated even though the error is being logged.