public void LoadFromXml(XElement xElement)
        {
            CatalogItems = new List<CatalogItem>();

            foreach (XElement catalogElements in xElement.Elements("CatalogItems"))
            {
                foreach (XElement catalogItemElement in catalogElements.Elements("CatalogItem") )
                {
                    CatalogItem newItem = new CatalogItem();

                    newItem.LoadFromXml(catalogItemElement);

                    CatalogItems.Add(newItem);
                }
            }

            foreach (XElement catalogElements in xElement.Elements("BoxedItems"))
            {
                foreach (XElement catalogElement in catalogElements.Elements("BoxedItem"))
                {
                    BoxedItem newItem = new BoxedItem();

                    newItem.LoadFromXml(catalogElement);

                    BoxedItems.Add(newItem);
                }
            }

            foreach (XElement catalogElements in xElement.Elements("VolumeItems"))
            {
                foreach (XElement catalogElement in catalogElements.Elements("VolumeItem"))
                {
                    VolumeItem newItem = new VolumeItem();

                    newItem.LoadFromXml(catalogElement);

                    VolumeItems.Add(newItem);
                }
            }
        }
        CatalogItem CreateNewCatalogItem()
        {
            CatalogItem catalogItem = new CatalogItem();

            if (rdoCatalogBox.Checked)
            {
                catalogItem = new BoxedItem();
            }
            else if (rdoCatalogVolume.Checked)
            {
                catalogItem = new VolumeItem();
            }
            else
            {
                catalogItem = new CatalogItem();
            }

            return catalogItem;
        }