transform: rotate(180deg);
 

private RadWorksheetEditor activeWorksheetEditor;

public MainWindow()
{
  InitializeComponent();

  this.spreadsheet.ActiveSheetEditorChanged += (s, e) =>
  {
 if (activeWorksheetEditor != null)
 {
 activeWorksheetEditor.Selection.SelectionChanged -= Selection_SelectionChanged;
 }

 activeWorksheetEditor = this.spreadsheet.ActiveWorksheetEditor;
 activeWorksheetEditor.Selection.SelectionChanged += Selection_SelectionChanged;
  };
}

private void Selection_SelectionChanged(object? sender, EventArgs e)
{
  this.spreadsheet.ActiveWorksheetEditor.Selection.FillSelection.IsEnabled = true;
}

static MainWindow()
{
    EventManager.RegisterClassHandler(typeof(RadMenuItem), PreviewMouseLeftButtonUpEvent, new MouseButtonEventHandler(OnRadMenuItemPreviewMouseLeftButtonUp), true);
}

private static void OnRadMenuItemPreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{
    RadMenuItem radMenuItem = (RadMenuItem)sender;

    RadContextMenu radContextMenu = radMenuItem.ParentOfType<RadContextMenu>();

    if (radContextMenu != null)
    {
        PropertyInfo menuPropertyInfo = radMenuItem.GetType().GetProperty("Menu", BindingFlags.Public | BindingFlags.Instance);
        if (menuPropertyInfo != null)
        {
            MethodInfo setMethod = menuPropertyInfo.GetSetMethod(true);
            if (setMethod != null)
            {
                Application.Current.Dispatcher.BeginInvoke(new Action(() =>
                {
                    setMethod.Invoke(radMenuItem, new object[] { radContextMenu });
                }), System.Windows.Threading.DispatcherPriority.Background);
            }
        }
    }
}

 var cells = radDocument.EnumerateChildrenOfType<Telerik.Windows.Documents.Model.TableCell>();
 foreach (var cell in cells)
 {
     cell.Padding = new Padding(10);
 }