/QDFeedParser/Xml/XpathFeedXmlParser.cs

using System;

using System.Collections.Generic;

using System.Xml;

using System.Xml.XPath;

using System.Text;



namespace QDFeedParser.Xml

{

    public class XPathFeedXmlParser : FeedXmlParserBase

    {

        #region IFeedXmlParser Members



        public override void ParseFeed(IFeed feed, string xml)

        {

            switch (feed.FeedType)

            {

                case FeedType.Rss20:

                    var rssFeed = feed as Rss20Feed;

                    ParseRss20Header(rssFeed, xml);

                    ParseRss20Items(rssFeed, xml);

                    break;

                case FeedType.Atom10:

                    var atomFeed = feed as Atom10Feed;

                    ParseAtom10Header(atomFeed, xml);

                    ParseAtom10Items(atomFeed, xml);

                    break;

            }

        }

        

        public override FeedType CheckFeedType(string feedxml)

        {

            var doc = new XmlDocument();

            doc.LoadXml(feedxml);

            var xmlRootElement = doc.DocumentElement;

            if (xmlRootElement.Name.Contains(RssRootElementName) && xmlRootElement.GetAttribute(RssVersionAttributeName) == "2.0")

                return FeedType.Rss20;

            else if (xmlRootElement.Name.Contains(AtomRootElementName))

                return FeedType.Atom10;

            else

                throw new InvalidFeedXmlException("Unable to determine feedtype (but was able to parse file) for feed");

        }



        #endregion



        #region Atom 1.0 parsing methods



        private XmlNamespaceManager NsManager;



        private void ParseAtom10Header(Atom10Feed atomFeed, string xml)

        {

            var xmlDoc = new XmlDocument();

            xmlDoc.LoadXml(xml);



            //Initialize our namespace manager.

            NsManager = new XmlNamespaceManager(xmlDoc.NameTable);

            NsManager.AddNamespace("atom", "http://www.w3.org/2005/Atom");



            var titleNode = xmlDoc.SelectSingleNode("/atom:feed/atom:title", NsManager);

            atomFeed.Title = titleNode.InnerText;



            var linkNode = xmlDoc.SelectSingleNode("/atom:feed/atom:link[not(@rel)]/@href", NsManager) ??

                           xmlDoc.SelectSingleNode("/atom:feed/atom:author/atom:uri", NsManager) ??

                           xmlDoc.SelectSingleNode("/atom:feed/atom:link[@rel='alternate']/@href", NsManager);



            atomFeed.Link = linkNode == null ? string.Empty : linkNode.InnerText;



            var dateTimeNode = xmlDoc.SelectSingleNode("/atom:feed/atom:updated", NsManager);



            DateTime timeOut;

            DateTime.TryParse(dateTimeNode.InnerText, out timeOut);

            atomFeed.LastUpdated = timeOut.ToUniversalTime();



            var generatorNode = xmlDoc.SelectSingleNode("/atom:feed/atom:generator", NsManager);

            atomFeed.Generator = generatorNode == null ? string.Empty : generatorNode.InnerText;

        }



        private void ParseAtom10Items(IFeed feed, string xml)

        {

            var xmlDoc = new XmlDocument();

            xmlDoc.LoadXml(xml);

            var feedItemNodes = xmlDoc.SelectNodes("/atom:feed/atom:entry", NsManager);

            foreach(XmlNode node in feedItemNodes)

            {

                feed.Items.Add(ParseAtom10SingleItem(node));

            }

        }



        private BaseFeedItem ParseAtom10SingleItem(XmlNode itemNode)

        {

            var titleNode = itemNode.SelectSingleNode("atom:title", NsManager);

            var datePublishedNode = itemNode.SelectSingleNode("atom:updated", NsManager);

            var authorNode = itemNode.SelectSingleNode("atom:author/name", NsManager);

            var idNode = itemNode.SelectSingleNode("atom:id", NsManager);

            var contentNode = itemNode.SelectSingleNode("atom:content", NsManager);

            var linkNode = itemNode.SelectSingleNode("atom:link/@href", NsManager);



            BaseFeedItem item = new Atom10FeedItem

            {

                Title = titleNode == null ? string.Empty : titleNode.InnerText,

                DatePublished = datePublishedNode == null ? DateTime.UtcNow : SafeGetDate(datePublishedNode.InnerText),

                Author = authorNode == null ? string.Empty : authorNode.InnerText,

                Id = idNode == null ? string.Empty : idNode.InnerText,

                Content = contentNode == null ? string.Empty : contentNode.InnerText,

                Link = linkNode == null ? string.Empty : linkNode.InnerText

            };



            var categoryNodes = itemNode.SelectNodes("atom:category/atom:term", NsManager);

            if (categoryNodes != null)

            {

                foreach (XmlNode categoryNode in categoryNodes)

                {

                    item.Categories.Add(categoryNode.InnerText);

                }

            }



            return item;

        }



        #endregion



        #region RSS 2.0 parsing methods



        private void ParseRss20Header(Rss20Feed rssFeed, string xml)

        {



            var xmlDoc = new XmlDocument();

            xmlDoc.LoadXml(xml);

            var titleNode = xmlDoc.SelectSingleNode("/rss/channel/title");

            rssFeed.Title = titleNode.InnerText;



            var descriptionNode = xmlDoc.SelectSingleNode("/rss/channel/description");

            rssFeed.Description = descriptionNode == null ? string.Empty : descriptionNode.InnerText;



            var linkNode = xmlDoc.SelectSingleNode("/rss/channel/link");

            rssFeed.Link = linkNode == null ? string.Empty : linkNode.InnerText;



            var dateTimeNode = xmlDoc.SelectSingleNode("//pubDate[1]");

            if (dateTimeNode == null) //We have to have a date, so we'll use the date/time when we polled the RSS feed as the default.

            {

                rssFeed.LastUpdated = DateTime.UtcNow;

            }

            else

            {

                DateTime timeOut;

                DateTime.TryParse(dateTimeNode.InnerText, out timeOut);

                rssFeed.LastUpdated = timeOut.ToUniversalTime();

            }



            var generatorNode = xmlDoc.SelectSingleNode("/rss/channel/generator");

            rssFeed.Generator = generatorNode == null ? string.Empty : generatorNode.InnerText;



            var languageNode = xmlDoc.SelectSingleNode("/rss/channel/language");

            rssFeed.Language = languageNode == null ? string.Empty : languageNode.InnerText;

        }



        private void ParseRss20Items(IFeed feed, string xml)

        {

            var xmlDoc = new XmlDocument();

            xmlDoc.LoadXml(xml);

            var feedItemNodes = xmlDoc.SelectNodes("/rss/channel/item");

            foreach (XmlNode item in feedItemNodes)

            {

                feed.Items.Add(ParseRss20SingleItem(item));

            }

        }



        private BaseFeedItem ParseRss20SingleItem(XmlNode itemNode)

        {

            var titleNode = itemNode.SelectSingleNode("title");

            var datePublishedNode = itemNode.SelectSingleNode("pubDate");

            var authorNode = itemNode.SelectSingleNode("author");

            var commentsNode = itemNode.SelectSingleNode("comments");

            var idNode = itemNode.SelectSingleNode("guid");

            var contentNode = itemNode.SelectSingleNode("description");

            var linkNode = itemNode.SelectSingleNode("link");



            BaseFeedItem item = new Rss20FeedItem

            {

                Title = titleNode == null ? string.Empty : titleNode.InnerText,

                DatePublished = datePublishedNode == null ? DateTime.UtcNow : SafeGetDate(datePublishedNode.InnerText),

                Author = authorNode == null ? string.Empty : authorNode.InnerText,

                Comments = commentsNode == null ? string.Empty : commentsNode.InnerText,

                Id = idNode == null ? string.Empty : idNode.InnerText,

                Content = contentNode == null ? string.Empty : contentNode.InnerText,

                Link = linkNode == null ? string.Empty : linkNode.InnerText

            };



            var categoryNodes = itemNode.SelectNodes("category");

            if (categoryNodes != null)

            {

                foreach (XmlNode categoryNode in categoryNodes)

                {

                    item.Categories.Add(categoryNode.InnerText);

                }

            }



            return item;

        }



        #endregion

    }

}