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Nasıl Yapılır: DataTemplate ile Üretilen Öğeleri Bulma

This example shows how to find elements that are generated by a DataTemplate.

Örnek

In this example, there is a ListBox that is bound to some XML data:

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

The ListBox uses the following DataTemplate:

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

If you want to retrieve the TextBlock element generated by the DataTemplate of a certain ListBoxItem, you need to get the ListBoxItem, find the ContentPresenter within that ListBoxItem, and then call FindName on the DataTemplate that is set on that ContentPresenter. The following example shows how to perform those steps. For demonstration purposes, this example creates a message box that shows the text content of the DataTemplate-generated text block.

            ' 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)
// 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);

The following is the implementation of FindVisualChild, which uses the VisualTreeHelper methods:

        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
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;
}

Ayrıca bkz.

Görevler

Nasıl Yapılır: ControlTemplate'den Oluşturulan Öğeleri Bulma

Kavramlar

Veri Bağlama Genel Bakış

Stillendirme ve Şablon Oluşturma

WPF XAML Ad Kapsamları

WPF içinde ağaçlar

Diğer Kaynaklar

Veri Bağlama Nasıl Yapılır Konuları