How to get list of categories and Keyword as a single XML | TOM API | R5.3

Question

I am using TOM APIs and trying to save list of categories and keywords as a single list. I am using

 Publication pub = tdse.GetPublication(publicationUri);
            ListRowFilter rowFilter = tdse.CreateListRowFilter();
            rowFilter.SetCondition("ItemType", ItemType.ItemTypeCategory | ItemType.ItemTypeKeyword);
            rowFilter.SetCondition("Recursive", true);

            catandkeyList.LoadXml(pub.GetListItems(ListColumnFilter.XMLListDefault, rowFilter));
            catandkeyList.Save(Server.MapPath("Keyworddetails.xml"));

But only list of categories are getting saved as a result. Can some one suggest if there is any other way to setCondition for Row filter for both Categories and keywords?

 rowFilter.SetCondition("ItemType", ItemType.ItemTypeCategory | ItemType.ItemTypeKeyword);

I only have publication ID as input parameter.