public void AddBus(DO.Bus bus) { XElement bussRootElem; try { bussRootElem = XmlTools.LoadListFromXMLElement(bussPath); } catch (DO.XmlFileLoadCreateException ex) { throw ex; } var temp = (from b in bussRootElem.Elements() where b.Element("LicenseNum").Value == bus.LicenseNum.ToString() select b).FirstOrDefault(); if (temp != null) { if (!bool.Parse(temp.Element("IsDeleted").Value)) { throw new DO.BadBusException(bus.LicenseNum, "Duplicate License number of bus"); } } bussRootElem.Add(XmlTools.CreateElement(bus)); XmlTools.SaveListToXMLElement(bussRootElem, bussPath); }