In this recipe, we will learn how to consume RSS feeds. RSS (Really Simple Syndication) feeds are published by many news agencies and informational websites such as CNN. RSS/ATOM is also used extensively in publishing blogs. RSS is based on XML format.
Let's try to check what is published at a CNN feed first. There are many feeds available at CNN. We will use one feed that returns the Top Stories. Check the following URL: http://rss.cnn.com/rss/cnn_topstories.rss. You should get content similar to that shown in the following screenshot, which contains the name of the top story with a link, posted date, and short description:
The following is the partial XML feed:
<?xml-stylesheet type="text/xsl" media="screen" href="/~d/styles/rss2full.xsl"?> <?xml-stylesheet type="text/css" media="screen" href="http://rss.cnn.com/~d/styles/itemcontent.css"?> <rss xmlns:media="http://search.yahoo.com/mrss/" xmlns:feedburner="http://rssnamespace.org/feedburner/ext/1.0" version="2.0"> <channel> <title>CNN.com</title> <link>http://www.cnn.com/?eref=rss_topstories</link> <description>CNN.com delivers up-to-the-minute news and information on the latest top stories, weather, entertainment, politics and more.</description> <language>en-us</language> <copyright>� 2011 Cable News Network LP, LLLP.</copyright> <pubDate>Sun, 24 Jul 2011 23:16:13 EDT</pubDate> <ttl>5</ttl> <image> <title>CNN.com</title> <link>http://www.cnn.com/?eref=rss_topstories</link> <url>http://i2.cdn.turner.com/cnn/.element/img/1.0/logo/ cnn.logo.rss.gif</url> <width>144</width> <height>33</height> <description>CNN.com delivers up-to-the-minute news and information on the latest top stories, weather, entertainment, politics and more.</description> </image> ... ...
In this recipe, we will create an application that will have a textbox to collect any RSS feed link and display the updates from the feed provider. Also, when you click the item in the list box you will be directed to the site to display the details.
- Open a new project and create a new Phone 7 Application with the name
Recipe1_RssReader. - Add a new class to the project with the name
RssFeed.cs. Open the file and add a new classRssFeedto collect the feed data:public class RssFeed { public string Title { get; set; } public string Content { get; set; } public DateTime DatePosted { get; set; } public Uri URL { get; set; } } - Open the
MainPage.xamlfile and add three rows with twoTextBlockcontrols and aHyperlinkButton:<Grid x:Name="ContentPanel2" Margin="12,217,12,-13" Grid.Row="1"> <ListBox x:Name ="lstItems" Margin="0,6,0,0"> <ListBox.ItemTemplate> <DataTemplate> <Grid> <Grid.RowDefinitions> <RowDefinition /> <RowDefinition /> <RowDefinition /> </Grid.RowDefinitions> <StackPanel VerticalAlignment="Top"> <TextBlock Grid.Row="0" Text="{Binding Title}" FontWeight="Bold" Foreground="OrangeRed"/> <TextBlock Grid.Row="1" Text="{Binding Content}" /> <HyperlinkButton TargetName="_blank" Grid.Row="2" Name="DetailLink" Content="Details..." NavigateUri="{Binding URL}" Foreground="Yellow" HorizontalAlignment="Left"/> </StackPanel> </Grid> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </Grid> - Open the
MainPage.xaml.csfile. As we are going to use LINQ to XML, let's add a reference to the assemblySystem.Xml.Linqto the project, and then add theusingdeclarative at the beginning of the file:using System.Xml.Linq;
- Add code to initialize the
WebClientobject and theDownloadStringCompletedevent handler as shown in the following partial code snippet:public partial class MainPage : PhoneApplicationPage { // Constructor WebClient remoteXml; public MainPage() { InitializeComponent(); remoteXml = new WebClient(); remoteXml.DownloadStringCompleted += new DownloadStringCompletedEventHandler (remoteXml_DownloadStringCompleted); } … - Now add the
DownloadStringCompletedevent method. In this method, we download the XML file into theXDocumentobject and then using LINQ to XML we parse the three elements we need to save:private void remoteXml_DownloadStringCompleted(object sender, DownloadStringCompletedEventArgs e) { if (e.Error != null) return; XDocument xdoc = XDocument.Parse(e.Result); List<RssFeed> rssFeeds; rssFeeds = (from item in xdoc.Descendants("item") select new RssFeed() { Title = item.Element("title").Value, Content = item.Element("description").Value, URL = new Uri(item.Element("link").Value, UriKind.Absolute), }).ToList(); lstItems.ItemsSource = rssFeeds; } - Now add the button event handler to navigate to the feed URL:
private void button1_Click(object sender, RoutedEventArgs e) { string txtUri = textBox1.Text; txtUri = Uri.EscapeUriString(txtUri); Uri uri = new Uri(txtUri,UriKind.Absolute); remoteXml.DownloadStringAsync(uri); } - Press F5 and as we have embedded a CNN feed link, just click on Go and you should see the top stories feed displayed:
- Click on Details to launch the browser in order to see the details of the news item you selected from the feed items online.
For navigating to RSS feeds, we basically have two choices in Phone 7: one is by using the WebClient and the other is HttpWebRequest. Here we use the WebClient.
In the DownloadStringCompleted method, we use XDocument to parse the remote RSS feed XML file. Once it is downloaded, we parse the XML using a LINQ to XML query. Based on the feed XML, we just collected three elements: title, description, and link.
For more information on the WebClient class check this MSDN site: http://msdn.microsoft.com/en-us/library/system.net.webclient(v=VS.95).aspx.