public void LoadFromXml(XElement xElement)
        {
            xElement.LoadObjectFromXml(Catalog, "Catalog");
            xElement.LoadObjectFromXml(Inventory, "Inventory");

            Suppliers = new List<Vendor>();

            foreach (XElement suppliersElement in xElement.Elements("Suppliers"))
            {
                foreach (XElement vendorElement in suppliersElement.Elements("Vendor"))
                {
                    Vendor vendor = new Vendor();
                    vendor.LoadFromXml(vendorElement);
                    Suppliers.Add(vendor);
                }
            }

            SetVendors();
            SetInventoryItems();
        }