XmlDataProvider filtrage ChildNodes de l'élément sélectionné

Question

J'utilise XmlDataProvider pour lier certains contrôles d'interface utilisateur avec du contenu de fichier XML. Dans le code suivant, le DataGrid affiche la liste des instructions dans le fichier XML. J'ai deux ComboBox. Le premier ComboBox doit contenir les nœuds enfants de l'instruction sélectionnée (dans le DataGrid) ayant l'attribut Direction égal à Input.

Le second ComboBox devrait contenir les nœuds enfants de l'instruction sélectionnée (dans le DataGrid) ayant l'attribut Direction égal à Output.

Mon problème est que je suis incapable de trouver l'expression XPath nécessaire pour remplir la ItemsSource des contrôles ComboBox afin d'obtenir ce que je veux. En fait, il affiche tous les ChildNodes dans les deux comboBox.

Voici le balisage XAML:

<Window x:Class="XmlProviderDataGrid.MainWindow" 
     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" 
     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" 
     Title="MainWindow" Height="350" Width="525"> 

    <Window.Resources> 
     <DataTemplate x:Key="ParamterTemplate"> 
      <StackPanel Orientation="Horizontal"> 
       <TextBlock Margin="3" Text="Name: "/> 
       <TextBlock Margin="3" Text="{Binding XPath=@Name}"/> 
       <TextBlock Margin="3" Text="-"/> 
       <TextBlock Margin="3" Text="DataType: "/> 
       <TextBlock Margin="3" Text="{Binding XPath=@DataType}"/> 
       <TextBlock Margin="3" Text="-"/> 
       <TextBlock Margin="3" Text="Direction: "/> 
       <TextBlock Margin="3" Text="{Binding XPath=@Direction}"/> 
      </StackPanel> 
     </DataTemplate> 
    </Window.Resources> 

    <Grid ShowGridLines="True"> 
     <Grid.DataContext> 
      <XmlDataProvider Source="XMLMapping.xml" XPath="InstructionsMapping/Instruction"/> 
     </Grid.DataContext> 
     <Grid.RowDefinitions> 
      <RowDefinition Height="150*" /> 
      <RowDefinition Height="181*" /> 
      <RowDefinition Height="181*" /> 
     </Grid.RowDefinitions> 

     <Grid.ColumnDefinitions> 
      <ColumnDefinition Width="250*"/> 
      <ColumnDefinition Width="260*" /> 
     </Grid.ColumnDefinitions> 

     <DataGrid x:Name="dataGrid1" Margin="8,8,8,0" Grid.Row="0" Grid.ColumnSpan="2" 
      AutoGenerateColumns="False" ItemsSource="{Binding}" 
      Height="100" VerticalAlignment="Top" 
      IsSynchronizedWithCurrentItem="True"> 
      <DataGrid.Columns> 
       <DataGridTextColumn Binding="{Binding XPath=@Name}" Header="Name"/> 
       <DataGridTextColumn Binding="{Binding XPath=@ConvertedFrom}" Header="ConvertedFrom"/> 
       <DataGridTextColumn Binding="{Binding XPath=@InstType}" Header="Type"/> 
       <DataGridTextColumn Binding="{Binding XPath=@Data}" Header="Data file"/> 
       <DataGridTextColumn Binding="{Binding XPath=@Inputs}" Header="Inputs"/> 
      </DataGrid.Columns> 
     </DataGrid> 

     <Button Margin="5" VerticalAlignment="Top" Grid.Row="1" Grid.Column="0" Content="New Instruction" Click="OnCreateNewInstruction"/> 
     <Button Margin="5" VerticalAlignment="Top" Grid.Row="1" Grid.Column="1" Content="Edit Instruction" Click="OnEditNewInstruction"/> 


     <StackPanel Grid.Row="2" Grid.Column="1"> 
      <Label Background="Gray" FontSize="12" BorderBrush="Black" BorderThickness="1" FontWeight="Bold" >Output Parameters:</Label> 
      <ComboBox x:Name="lstOutput" Margin="5" VerticalAlignment="Top" HorizontalAlignment="Stretch" 
         ItemsSource="{Binding Path=SelectedItem, ElementName=dataGrid1, UpdateSourceTrigger=PropertyChanged}" 
         ItemTemplate ="{StaticResource ParamterTemplate}"      
         IsSynchronizedWithCurrentItem="True" Visibility="Visible"> 
      </ComboBox> 
     </StackPanel> 
     <StackPanel Grid.Row="2" Grid.Column="0"> 
     <Label Background="Gray" FontSize="12" BorderBrush="Black" BorderThickness="1" FontWeight="Bold" Grid.Column="0">Input Parameters:</Label> 
      <ComboBox x:Name="lstInput" Margin="5,5,5,5" VerticalAlignment="Top" HorizontalAlignment="Stretch" 
        ItemsSource="{Binding Path=SelectedItem, ElementName=dataGrid1, UpdateSourceTrigger=PropertyChanged}" 
        ItemTemplate ="{StaticResource ParamterTemplate}"      
        IsSynchronizedWithCurrentItem="True" Visibility="Visible"> 
      </ComboBox> 
     </StackPanel> 
     </Grid>  
</Window> 

Vous pouvez trouver mon fichier XML utilisé:

<?xml version="1.0" encoding="utf-8"?> 
<InstructionsMapping xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" CatalogID="Micro_8"> 
    <Instruction Name="XIC" ConvertedFrom="XIC" DataFilePath="\Project18_v1.7z"> 
    <Parameter Name="Out14" Direction="Output" DataType="Bool" /> 
    <Parameter Name="Out2" Direction="Output" DataType="Bool" /> 
    <Parameter Name="In3" Direction="Input" DataType="Real" /> 
    <Parameter Name="In11" Direction="Input" DataType="Real" /> 
    <Parameter Name="In13" Direction="Input" DataType="Dint" /> 
    </Instruction> 
    <Instruction Name="OTE" ConvertedFrom="OTE" DataFilePath="\Project18_v1.7z"> 
    <Parameter Name="In1" Direction="Input" DataType="Bool" /> 
    <Parameter Name="In2" Direction="Input" DataType="Dint" /> 
    <Parameter Name="In3" Direction="Input" DataType="Real" /> 
    <Parameter Name="Ou1" Direction="Output" DataType="Bool" /> 
    <Parameter Name="Out2" Direction="Output" DataType="Bool" /> 
    </Instruction> 
    <Instruction Name="TON" ConvertedFrom="TON" DataFilePath="\Project18_v1.7z"> 
    <Parameter Name="In1" Direction="Input" DataType="Bool" /> 
    <Parameter Name="In2" Direction="Input" DataType="Dint" /> 
    <Parameter Name="In3" Direction="Input" DataType="Real" /> 
    <Parameter Name="Ou1" Direction="Output" DataType="Bool" /> 
    <Parameter Name="Out2" Direction="Output" DataType="Bool" /> 
    </Instruction> 
    <Instruction Name="ADD" ConvertedFrom="+" DataFilePath="\Project18_v1.7z"> 
    <Parameter Name="In1" Direction="Input" DataType="Bool" /> 
    <Parameter Name="In2" Direction="Input" DataType="Real" /> 
    <Parameter Name="In3" Direction="Input" DataType="Real" /> 
    <Parameter Name="In4" Direction="Input" DataType="Real" /> 
    <Parameter Name="In5" Direction="Input" DataType="Bool" /> 
    </Instruction> 
    <Instruction Name="ADD" ConvertedFrom="+" DataFilePath="\Project18_v1.7z"> 
    <Parameter Name="In1" Direction="Output" DataType="Bool" /> 
    <Parameter Name="In2" Direction="Output" DataType="Bool" /> 
    <Parameter Name="In3" Direction="Output" DataType="Dint" /> 
    <Parameter Name="In4" Direction="Output" DataType="Bool" /> 
    <Parameter Name="In5" Direction="Output" DataType="Dint" /> 
    </Instruction> 
</InstructionsMapping> 

Answer 1

Une façon possible:

<ComboBox x:Name="lstInput" Margin="5,5,5,5" VerticalAlignment="Top" HorizontalAlignment="Stretch" 
     DataContext="{Binding Path=SelectedItem, ElementName=dataGrid1, UpdateSourceTrigger=PropertyChanged}" 
     ItemsSource="{Binding XPath=Parameter[@Direction\=\'Input\']}" 
     ItemTemplate ="{StaticResource ParamterTemplate}"      
     IsSynchronizedWithCurrentItem="True" Visibility="Visible"> 
</ComboBox>