/// <summary>
        ///
        /// </summary>
        /// <param name="entryEl"></param>
        /// <param name="nsMgr"></param>
        /// <param name="rel"></param>
        /// <param name="contentType">e.g. application/atom+xml</param>
        /// <param name="contentSubType">e.g. "entry"</param>
        /// <param name="baseUri"></param>
        /// <returns></returns>
        public static string GetLink(IXmlNode entryEl, XmlNamespaceManager nsMgr, string rel, string contentType, string contentSubType, Uri baseUri)
        {
            Debug.Assert(contentSubType == null || contentType != null, "contentSubType is only used if contentType is also provided");

            string xpath = string.Format(CultureInfo.InvariantCulture,
                                         @"atom:link[@rel='{0}']",
                                         rel);

            foreach (XmlElement link in entryEl.SelectNodesNS(xpath, nsMgr.ToNSMethodFormat()))
            {
                if (contentType != null)
                {
                    string mimeType = link.GetAttribute("type");
                    if (mimeType == null || mimeType == "")
                    {
                        continue;
                    }
                    IDictionary mimeData = MimeHelper.ParseContentType(mimeType, true);
                    if (contentType != (string)mimeData[""])
                    {
                        continue;
                    }
                    if (contentSubType != null && contentSubType != (string)mimeData["type"])
                    {
                        continue;
                    }
                }
                return(XmlHelper.GetUrl(link, "@href", baseUri));
            }
            return("");
        }
            public override void RemoveAllCategories(IXmlNode node, string categoryScheme, Uri documentUri)
            {
                if (categoryScheme == null)
                {
                    return;
                }

                XmlNamespaceManager nsMgr = new XmlNamespaceManager(new NameTable());

                nsMgr.AddNamespace("atom", NamespaceUri);
                ArrayList nodesToRemove = new ArrayList();

                foreach (XmlElement categoryEl in node.SelectNodesNS("atom:category", nsMgr.ToNSMethodFormat()))
                {
                    string scheme = categoryEl.GetAttribute("scheme");
                    if (SchemesEqual(scheme, categoryScheme))
                    {
                        nodesToRemove.Add(categoryEl);
                    }
                }
                foreach (XmlElement categoryEl in nodesToRemove)
                {
                    categoryEl.ParentNode.RemoveChild(categoryEl);
                }
            }