private void ribbonControl1_SizeChanged(object sender, EventArgs e)
        {
            RibbonControl ribbon=sender as RibbonControl;
            foreach (Control  p in ribbon.Controls)
            {
                if (p is RibbonPanel)
                {
                    p.Height = ribbon.Height - 60;
                    p.Width = ribbon.Width - 6;
                    foreach (Control subitem in p.Controls)
                    {
                        if (subitem.Dock == DockStyle.Fill)
                        {
                            subitem.Refresh();
                        }
                    }
                }
            }
        }