If you are like me you probably have a hard time finding something to create when trying out new stuff.  This time I sat down and tried to figure out something to use LINQ and Silverlight for and maybe WCF, WPF and Ajax as well. At the time I was watching TV and the EPG (Electronic Programming Guide) didn’t work, so I started to look for a web site with a program guide supporting reminders and other nice features to let you know what’s on TV. I didn’t find anything good.
I then started to look for an xml/text format for TV programs. I did some searching and came across xmltv. Nice! I now had an xml source looking something like this:

<tv>
  <channel id="channel1">    
    <display-name lang="nb">Channel 1</display-name>
  </channel>
  <channel id="channel2">
    <display-name lang="en">Channel 2</display-name>
  </channel>
  ...
  <programme start="20070801033000 +0200" stop="20070801053000 +0200" channel="channel1">
    <title lang="nb">Program 1</title>
    <desc lang="nb">Program description.</desc>
    <credits>
      <director>...</director>
      <actor>...</actor>
      <actor>...</actor>
    </credits>
    <date>2004</date>
    <category lang="en">movie</category>
    <category lang="en">drama</category>
  </programme>
  ...
</tv>

So now I had an xml document containing all the data I needed and this was a perfect time to try out XLINQ. I decided to stick with the LINQ query syntax and not mix in Lambda expressions to keep things simple and readable. I came up with this expression to get all TV channels:

public List<TvChannel> GetTvChannelsWithoutGuide()
{
    IEnumerable<TvChannel> channels;
    try
    {
        XElement tvGuide = XElement.Load(_xmlFileLoc);

	channels = from c in tvGuide.Descendants("channel")
		   orderby (string)c.Element("display-name") ascending
		   select new TvChannel
		   {
		       Id = (string)c.Attribute("id"),
		       Name = (string)c.Element("display-name"),
		       Lang = (string)c.Element("display-name").Attribute("lang"),
		       TvGuideLoaded = false
		   };
    }
    catch (FileNotFoundException fileNotFoundEx)
    {
        throw new FileNotFoundException(string.Format("Xml file for tv guide not found at {0}",
						      _xmlFileLoc), fileNotFoundEx);
    }
    return channels.ToList<TvChannel>();
}

The XElement gives me the complete xml document that I can use XLINQ expressions on. In my query I’m looking only for TV channels, so I specify that in the query by

    from c in tvGuide.Descendants("channel")

This gives my a variable c that I use in my orderby clause and select statement. The orderby clause

    orderby (string)c.Element("display-name") ascending

uses the c variable to access the “display-name” element to set order by. But it’s the select statement which is the cool thing here! First here a listing of the TvChannel class:

[Serializable]
public class TvChannel
{
    public string Id { get; set; }
    public string Name { get; set; }
    public string Lang { get; set; }

    [XmlIgnore]
    public IEnumerable<TvProgramme> TvGuideNonSerializable {
        get { return TvGuide; }
        set { TvGuide = value.ToList(); } 
    }

    public List<TvProgramme> TvGuide
    {
        get;
        set;
    }
    public bool TvGuideLoaded { get; set; }
} 

Ignore the TvGuideNonSerializable property for now. By using select new TvChannel I can create an object of my TvChannel class an assign data from the xml document to my properties. I just love this syntax! It’s really nice and easally understandable. Another cool feature (running VS 2008 Beta 2) is that you get ItelliSense in LINQ for your classes, like this:



I also created other methods for retrieving all programs for one channel, all channels etc. At the time of writing I’m working on a Silverlight implementation for the TvGuide which I hopefully can show you soon. And later I’ll make all source code available.