Application.IsMenuGroupLoaded("xxx")
var AXAPP = (_AxApp.AcadApplication)_AcAp.Application.AcadApplication; // COM
for (int iMenuGroup = 0; iMenuGroup < AXAPP.MenuGroups.Count - 0; iMenuGroup++)
{
if (AXAPP.MenuGroups.Item(iMenuGroup).Name == "xxx")
{
_AcAp.Application.ShowAlertDialog("The ribbon is already loaded.");
bLoadCUI = false;
break;
}
}