private static void VisitCategoryElement(XmlReader reader, AtomEntryBase entry)
        {
            var category = new AtomCategory
                {
                    Term = reader.GetAttribute("term"),
                    Scheme = reader.GetAttribute("scheme"),
                    Label = reader.GetAttribute("label")
                };
            entry.AddCategory(category);

            if (reader.IsEmptyElement)
                return;

            while (reader.Read())
                if (reader.Name.Equals("category") && reader.NodeType == XmlNodeType.EndElement)
                    break;
        }
 internal void AddCategory(AtomCategory category)
 {
     _categories.Add(category);
 }