Technically, that property returns the state of that component/control. In
the case of controls on a usercontrol they are in runmode since there is no
designer/site associated with the controls. If you really need to know if
any control in the parent chain is in design mode, you can walk up the
parent chain, checking to see if the Site is non-null and if so, checking
the designmode property of the site.
e.g.
 public static bool IsDesignMode(Control control)
 {
  if (control == null)
   return false;

  if (control.Site != null && control.Site.DesignMode)
   return true;

  return IsDesignMode(control.Parent);
 }