.NET Rocker

The XmlDataProvider class enables Binding to XML inside XAML. This will allow you to bind e.g. to the rss feed of a blog like http://www.thomasclaudiushuber.com/blog/feed/, cause rss is simple XML.

A XmlDataProvider-Element is declared as a logic resource. You simply set the Source-Property to a XML-Document and optionally set the XPath-Property. The default value of the IsAsynchronous-Property of the XmlDataProvider is true, so your client won’t freeze if you specify a url as the source.

The following XAML creates a simple rss-reader. The root is a Window object that contains a XmlDataProvider inside its Resources-Property. The XmlDataProvider loads the feed of this blog and its XPath-Property points to the blogs items. The elements inside the Window are indirectly bound to the XmlDataProvider. They use the DataContext specified on the DockPanel. The special thing of the Bindings on this elements is that they do not directly point to the XmlDataProvider. Instead the Bindings start at the /rss/channel/item like specified in the XPath-Property of the XmlDataProvider. If you want to point directly to the XmlDataProvider-object, you’ve to set the BindsDirectlyToSource-Property of the Binding to true. This is used by the first TextBox. It allows the user to change the Source-Property of the XmlDataProvider to navigate to another feed like http://blog.trivadis.com/blogs/MainFeed.aspx. The Binding for this TextBox also specifies that the UpdateSourceTrigger is PropertyChanged. Without this, the Source would be updated on LostFocus, cause the TextBox.TextProperty has specified this behaviour in its metadata.

<Window x:Class="SimpleRssReader.Window1"
  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/…"
  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
  Title="RSS Reader" Height="600" Width="800">
 <Window.Resources>
  <XmlDataProvider x:Key="blog"
   Source="http://www.thomasclaudiushuber.com/blog/feed/"
   XPath="/rss/channel/item"/>
 </Window.Resources>
 <DockPanel
   DataContext="{Binding Source={StaticResource blog}}">
  <StackPanel DockPanel.Dock="Top"
    TextElement.FontWeight="Bold" Background="LightGray">
   <TextBlock Text="{Binding XPath=./../title}"
     FontSize="20" Margin="10 10 10 0"/>
    <TextBlock Text="{Binding XPath=./../description}"
      FontSize="10" FontWeight="Normal" Margin="10 0"/>
   <TextBox Margin="5" Text="{Binding
     Source={StaticResource blog},
     BindsDirectlyToSource=True,
     Path=Source,
     UpdateSourceTrigger=PropertyChanged}"/>
 </StackPanel>

  <StatusBar DockPanel.Dock="Bottom">
   <StatusBarItem Content="{Binding XPath=title}"/>
   <Separator/>
   <StatusBarItem Content="{Binding XPath=pubDate}"/>
  </StatusBar>

  <Grid>
   <Grid.ColumnDefinitions>
    <ColumnDefinition Width="308"/>
    <ColumnDefinition Width="Auto"/>
    <ColumnDefinition/>
   </Grid.ColumnDefinitions>

   <GroupBox Header="Blog-Eintr?ge">
    <ListBox IsSynchronizedWithCurrentItem="True"
      ItemsSource="{Binding}" DisplayMemberPath="title"/>
   </GroupBox>

   <GridSplitter Grid.Column="1"
     HorizontalAlignment="Center" Width="10"/>

   <Frame Grid.Column="2" Source="{Binding XPath=link}"/>
  </Grid>

 </DockPanel>
</Window>

To test the rss reader yourself, simply create a new WPF-Application Project and paste the XAML above into the Window1.xaml. You have just to set the value of the x:Class-Attribut on the Window-Element so that it matches your class in the Codebehind-File. The Codebehind-File itself doesn’t need any logic. The reader looks like this: