я решил это с помощью coldandtired :-)
если бы я мог, я бы отметил ваш ответ как полезный ;-)
ниже рабочего кода:
<HierarchicalDataTemplate DataType="cards" ItemsSource="{Binding XPath=card}">
<TextBox Text="somethings" />
</HierarchicalDataTemplate>
<HierarchicalDataTemplate DataType="card">
<StackPanel>
<TextBlock Text="{Binding XPath=@name}"/>
<TextBlock Text="{Binding XPath=question}"/>
<TextBlock Text="{Binding XPath=answer}" Margin="0,0,0,15"/>
</StackPanel>
</HierarchicalDataTemplate>
...
..
..
<XmlDataProvider x:Key="dataxml" XPath="root/cards" Source="folder\cards.xml" />
<Label Height="28" Content="Frage:" Margin="0,0,0,177" />
<TextBox DataContext="{Binding ElementName=treeView, Path=SelectedItem}" Text="{Binding XPath=answer, UpdateSourceTrigger=PropertyChanged}" Margin="0,44,0,136" />
<Label Height="28" Content="Antwort:" Margin="0,102,0,94" />
<TextBox DataContext="{Binding ElementName=treeView, Path=SelectedItem}" Text="{Binding XPath=question, UpdateSourceTrigger=PropertyChanged}" Margin="0,136,0,0" />
</Grid>
<Grid>
<TreeView Name="treeView" ItemsSource="{Binding Source={StaticResource dataxml}, XPath=.}"/>
</Grid>