void RestoreDefaultProperties(object sender, RoutedEventArgs e)
{
    UIElementCollection uic = Sandbox.Children;
    foreach (Shape uie in uic)
    {
        LocalValueEnumerator locallySetProperties = uie.GetLocalValueEnumerator();
        while (locallySetProperties.MoveNext())
        {
            DependencyProperty propertyToClear = locallySetProperties.Current.Property;
            if (!propertyToClear.ReadOnly) { uie.ClearValue(propertyToClear); }
        }
    }
}