Binding to XMLDataProvider in Code Behind

i have a problem moving a XMLDataprovider Binding with XPath from Xaml to code behind.

Labels.xml

<?xml version="1.0" encoding="utf-8" ?>
<Labels>
  <btnOne Label="Button1"/>
  <btnTwo Label="Button2"/>开发者_StackOverflow社区;
</Labels>

MainWindow.xaml

<Window
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
     xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" mc:Ignorable="d" x:Class="bindings.MainWindow"
        Title="MainWindow" Height="350" Width="525">
    <Window.Resources>
        <XmlDataProvider x:Key="XMLLabels" Source="Labels.xml" XPath="Labels"/>
    </Window.Resources>
    <Grid>
        <Button Content="{Binding Source={StaticResource XMLLabels}, XPath=btnOne/@Label}" Height="23" HorizontalAlignment="Left" Margin="12,12,0,276" Name="btnOne" Width="75" />
        <Button Content="Button" Height="23" HorizontalAlignment="Left" Margin="93,12,0,276" Name="btnTwo" Width="75" Loaded="btnTwo_Loaded" />       
    </Grid>
</Window> 

MainWindow.xaml.cs

...
private void btnTwo_Loaded(object sender, RoutedEventArgs e)
{
    String Type = sender.GetType().Name;
    if (Type == "Button")
    {
        Button btn = sender as Button;
        Binding label = new Binding("XMLBind");
        XmlDataProvider xmlLabels = (XmlDataProvider)this.FindResource("XMLLabels");
        label.Source = xmlLabels;
        label.XPath = "btnTwo/@Header";
        btn.SetBinding(Button.ContentProperty, label);
    }
}
...

The binding to content of btnOne works as aspected "Button1". But btnTwo is set to an empty string. The Output shows no errors.

Thanks for any advice.

---

shouldn't

label.XPath = "btnTwo/@Header";

be

label.XPath = "btnTwo/@Label";