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Parse podcast RSS feed in C#

Posted on 2009-06-27
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1,687 Views
Last Modified: 2013-11-18
I am having some difficulty with podcast RSS feeds.  I am able to read the feed in and parse the tags without a problem, but I run into problems as I iterate through each item in the channel and trying to figure out which attribute actually has the link to the MP3.  

Some feeds use the link tag, others use the enclosure and then there are the itunes tags.  Is there any advice on the best way to handle this?

This is the code I'm currently working with.
if (string.IsNullOrEmpty(url))
                throw new ArgumentNullException("url");
 
           RSSFeed feed = new RSSFeed();
 
            try
            {
                string content = GetURLSource(url);
                XmlDocument rssDoc = new XmlDocument();
                rssDoc.LoadXml(content);
                XmlNodeList rssNodes = rssDoc.SelectNodes("/rss/channel/item");
 
                feed.Link = rssDoc.SelectSingleNode("/rss/channel/link") != null ? rssDoc.SelectSingleNode("/rss/channel/link").InnerText : string.Empty;
                feed.Title = rssDoc.SelectSingleNode("/rss/channel/title") != null ? rssDoc.SelectSingleNode("/rss/channel/title").InnerText : string.Empty;
                feed.Description = rssDoc.SelectSingleNode("/rss/channel/description") != null ? rssDoc.SelectSingleNode("/rss/channel/description").InnerText : string.Empty;
 
                if (rssNodes != null)
                    foreach (XmlNode node in rssNodes)
                    {
                        RSSEvent rssEvent = new RSSEvent
                        {
                            CopyRight = node.SelectSingleNode("copyright") != null ? node.SelectSingleNode("copyright").InnerText : string.Empty,
                            Description = node.SelectSingleNode("description") != null ? node.SelectSingleNode("description").InnerText : string.Empty,
                            Link = node.SelectSingleNode("link") != null ? node.SelectSingleNode("link").InnerText : string.Empty,
                            PubDate = node.SelectSingleNode("pubdate") != null ? node.SelectSingleNode("pubdate").InnerText : string.Empty,
                            Title = node.SelectSingleNode("title") != null ? node.SelectSingleNode("title").InnerText : string.Empty,
                            EnclosureUrl = node.SelectSingleNode("enclosure") != null ? node.SelectSingleNode("enclosure").Attributes["url"].InnerText : string.Empty,
                            EnclosureType = node.SelectSingleNode("enclosure") != null ? node.SelectSingleNode("enclosure").Attributes["type"].InnerText : string.Empty,
                            EnclosureLength = node.SelectSingleNode("enclosure") != null ? node.SelectSingleNode("enclosure").Attributes["length"].InnerText : string.Empty
                        };
 
                        feed.Events.Add(rssEvent);
                    }
            }
            catch (Exception ex)
            {
                throw new Exception(ex.Message, ex.InnerException);
            }
 
            return feed;

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Question by:andy_ee
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6 Comments
 
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Accepted Solution

by:
MogalManic earned 500 total points
ID: 24735277
Instead of doing an if for every node, I would try to determine the type and then delegate the parsing to the specific handler.  That way you will have only one logical expression and the code would be much easier to read.

Something like this:

 

  IRssHandler handler=null;
  if (rssDoc.SelectNodes(...)=="???")
    handler=new ITunesRSSHandler(rssDoc);
  else if (rssDoc.SelectNodes(...2)==""???2"
    handler - new PodCast1Handler(rssDoc)
  //......One if for each handler type
 
 feed=handler.parseFeed();
feed.Events.addRange(handler.ParseEvents());
 
 
//And one handler would look like this
public class PodCastHandler : IRSSHandler
{
    PodCastHandler(XmldDocument rssDoc)
    {
       //Initialze class...
       XmlNodeList rssNodes = rssDoc.SelectNodes("/rss/channel/item");
       //...
    }
 
    public Feed parseFeed()
    {
         RSSFeed feed = new RSSFeed();
 
         feed.Link = rssDoc.SelectSingleNode("/rss/channel/link").InnerText;
         feed.Title = rssDoc.SelectSingleNode("/rss/channel/title").InnerText;
         feed.Description = rssDoc.SelectSingleNode("/rss/channel/description").InnerText;
 
         return feed;
 
    }
 
    public RSSEvent[] parseEvents()
    {
       RssEvent[] events=null;
       if (rssNodes != null)
       {
          events=new RssEvents[rssNodes.Count];
          foreach (XmlNode node in rssNodes)
          {
               RSSEvent rssEvent = new RSSEvent
               CopyRight = node.SelectSingleNode("copyright").InnerText;
               //...Set Other properties...
               events[evtIdx++]=rssEvent;
          }
       }
       return events;
     }
}

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Author Comment

by:andy_ee
ID: 24735572
Excellent response.  However I need to find a clean way of differentiating between a podcast feed and an iTunes feed.
0
 

Author Comment

by:andy_ee
ID: 24735577
... also, you list an interface called IRssHandler.  Is there code for that please?
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LVL 21

Expert Comment

by:MogalManic
ID: 24735908
IRssHandler is the base interface for all of the "RSS Handlers".  It would look something like this:
public interface IRssHandler
{
    ///<Summary>Parse the root element of the feed and build a Feed object</Summary>
    public Feed parseFeed();
    ///<Summary>Parse the feed events into RSSEvent collection</Summary>
    public RSSEvent[] parseEvents();
}

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LVL 21

Expert Comment

by:MogalManic
ID: 24736307
To check if it is a iTunes feed you should just check to see if it has an itunes namespace.  Something like this:
if (rssDoc.DocumentElement.GetAttribute("xmlns:itunes")!="")
  handler=new iTunesRSSHandler(rssDoc);
else if //Other rss types here

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Author Closing Comment

by:andy_ee
ID: 31597638
Thanks!  Excellent advice.
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