private static void OnIsValidPropertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { DescriptionViewer dv = d as DescriptionViewer; if (dv != null && !dv.AreHandlersSuspended()) { dv.SetValueNoCallback(DescriptionViewer.IsValidProperty, e.OldValue); throw new InvalidOperationException(String.Format(CultureInfo.InvariantCulture, resources.UnderlyingPropertyIsReadOnly, "IsValid")); } }