WPF 多层绑定XML解决方法

WPF 多层绑定XML
XML文件

<?xml version="1.0" encoding="utf-8" ?>
<a>
  <b name="一" code="001">
    <c cname="一.1" code="001001" />
    <c cname="一.2" code="001002" />
    <c cname="一.3" code="001003" />

  </b>
  <b name="二" code="002" />
    <c cname="二.1" code="002001" />
    <c cname="二.2" code="002002" />
    <c cname="二.3" code="002003" />
</a>

test.xaml

<Window x:Class="Wpf1.test2"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="test2" Height="300" Width="300">
    <Window.Resources>
        <XmlDataProvider x:Key="xmldata" Source="data/x2.xml" XPath="a/b"/>
        <DataTemplate x:Key="dataTemplate2">
            <Grid Width="300">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="150"/>
                    <ColumnDefinition Width="150"/>
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition></RowDefinition>
                    <RowDefinition></RowDefinition>
                </Grid.RowDefinitions>
                <TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding XPath=@cname}" />
                <TextBlock Grid.Column="1" Grid.Row="0" Text="{Binding XPath=@code}" />
            </Grid>
        </DataTemplate>

        <DataTemplate x:Key="dataTemplate1">
            <Grid Width="300">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="150"/>
                    <ColumnDefinition Width="150"/>
                </Grid.ColumnDefinitions>

                <Grid.RowDefinitions>
                    <RowDefinition Height="15"/>
                    <RowDefinition/>
                </Grid.RowDefinitions>
                <TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding XPath=@name}" />
                <TextBlock Grid.Column="1" Grid.Row="0" Text="{Binding XPath=@code}" />
                <ListBox  ItemsSource="{Binding}" ItemTemplate="{StaticResource dataTemplate2}"
                  Grid.Column="0" Grid.Row="1"  Grid.ColumnSpan="2"/>
            </Grid>
        </DataTemplate>
    </Window.Resources>
    <Grid DataContext="{Binding Source={StaticResource xmldata}}" Width="310" >
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="150"/>
            <ColumnDefinition Width="150"/>
        </Grid.ColumnDefinitions>
        <Grid.RowDefinitions>
            <RowDefinition Height="15"/>
            <RowDefinition/>
        </Grid.RowDefinitions>

        <!--<Label>My Soccer Leagues</Label>-->
        <TextBlock Grid.Column="0" Grid.Row="0" Text="名称" />
        <TextBlock Grid.Column="1" Grid.Row="0" Text="code" />
 
        <DataGrid  ItemsSource="{Binding}"  Grid.Column="0" Grid.Row="1"  Grid.ColumnSpan="2">
            <DataGrid.Columns>
                <DataGridTextColumn Header="名称" HeaderTemplate="{StaticResource dataTemplate1}" />
            </DataGrid.Columns>
        </DataGrid>
    </Grid>
</Window>

为什么绑定只显示<b name="一" code="001">的子集， <b name="二"/>的不显示？
请高手指教

[解决办法]
试一试这样，修改xpath

<XmlDataProvider x:Key="xmldata" Source="data/x2.xml" XPath="a/b"/>
-->
<XmlDataProvider x:Key="xmldata" Source="data/x2.xml" XPath="a"/>

<TextBlock Grid.Column="0" Grid.Row="0" Text="{Binding XPath=@name}" />
-->
<TextBlock Grid.Column="1" Grid.Row="0" Text="{Binding XPath=b/@code}" />