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Instrucciones para buscar elementos DataTemplate-Generated

En este ejemplo se muestra cómo buscar elementos generados por .DataTemplate

Ejemplo

En este ejemplo, hay un ListBox que está enlazado a algunos datos XML.

<ListBox Name="myListBox" ItemTemplate="{StaticResource myDataTemplate}"
         IsSynchronizedWithCurrentItem="True">
  <ListBox.ItemsSource>
    <Binding Source="{StaticResource InventoryData}" XPath="Books/Book"/>
  </ListBox.ItemsSource>
</ListBox>

ListBox utiliza lo siguiente:DataTemplate

<DataTemplate x:Key="myDataTemplate">
  <TextBlock Name="textBlock" FontSize="14" Foreground="Blue">
    <TextBlock.Text>
      <Binding XPath="Title"/>
    </TextBlock.Text>
  </TextBlock>
</DataTemplate>

Si desea recuperar el TextBlock elemento generado por el DataTemplate de un determinado ListBoxItem, debe obtener ListBoxItem, buscar dentro ContentPresenter de ese ListBoxItemy, a continuación, llamar a FindName en el DataTemplate que se establece en ese ContentPresenter. En el ejemplo siguiente se muestra cómo realizar esos pasos. Para fines de demostración, en este ejemplo se crea un cuadro de mensaje que muestra el contenido de texto del DataTemplatebloque de texto generado.

// Getting the currently selected ListBoxItem
// Note that the ListBox must have
// IsSynchronizedWithCurrentItem set to True for this to work
ListBoxItem myListBoxItem =
    (ListBoxItem)(myListBox.ItemContainerGenerator.ContainerFromItem(myListBox.Items.CurrentItem));

// Getting the ContentPresenter of myListBoxItem
ContentPresenter myContentPresenter = FindVisualChild<ContentPresenter>(myListBoxItem);

// Finding textBlock from the DataTemplate that is set on that ContentPresenter
DataTemplate myDataTemplate = myContentPresenter.ContentTemplate;
TextBlock myTextBlock = (TextBlock)myDataTemplate.FindName("textBlock", myContentPresenter);

// Do something to the DataTemplate-generated TextBlock
MessageBox.Show("The text of the TextBlock of the selected list item: "
    + myTextBlock.Text);

' Getting the currently selected ListBoxItem
' Note that the ListBox must have
' IsSynchronizedWithCurrentItem set to True for this to work
Dim myListBoxItem As ListBoxItem = CType(myListBox.ItemContainerGenerator.ContainerFromItem(myListBox.Items.CurrentItem), ListBoxItem)

' Getting the ContentPresenter of myListBoxItem
Dim myContentPresenter As ContentPresenter = FindVisualChild(Of ContentPresenter)(myListBoxItem)

' Finding textBlock from the DataTemplate that is set on that ContentPresenter
Dim myDataTemplate As DataTemplate = myContentPresenter.ContentTemplate
Dim myTextBlock As TextBlock = CType(myDataTemplate.FindName("textBlock", myContentPresenter), TextBlock)

' Do something to the DataTemplate-generated TextBlock
MessageBox.Show("The text of the TextBlock of the selected list item: " & myTextBlock.Text)

A continuación se muestra la implementación de FindVisualChild, que usa los VisualTreeHelper métodos :

private childItem FindVisualChild<childItem>(DependencyObject obj)
    where childItem : DependencyObject
{
    for (int i = 0; i < VisualTreeHelper.GetChildrenCount(obj); i++)
    {
        DependencyObject child = VisualTreeHelper.GetChild(obj, i);
        if (child != null && child is childItem)
        {
            return (childItem)child;
        }
        else
        {
            childItem childOfChild = FindVisualChild<childItem>(child);
            if (childOfChild != null)
                return childOfChild;
        }
    }
    return null;
}

Private Function FindVisualChild(Of childItem As DependencyObject)(ByVal obj As DependencyObject) As childItem
    For i As Integer = 0 To VisualTreeHelper.GetChildrenCount(obj) - 1
        Dim child As DependencyObject = VisualTreeHelper.GetChild(obj, i)
        If child IsNot Nothing AndAlso TypeOf child Is childItem Then
            Return CType(child, childItem)
        Else
            Dim childOfChild As childItem = FindVisualChild(Of childItem)(child)
            If childOfChild IsNot Nothing Then
                Return childOfChild
            End If
        End If
    Next i
    Return Nothing
End Function

Consulte también