#1,190 – VisualChildrenCount and GetVisualChild

A FrameworkElement provides the VisualChildrenCount property and the GetVisualChild method, typically used during layout to walk through the child elements of the element participating in layout.  When you create a custom control that derives from FrameworkElement, you typically override both members, providing values that make sense for your control.

Below, we use these members to get a report of the visual children of a custom StackPanel.  (Because neither member is public, we override StackPanel to allow access).

XAML is:

    <StackPanel>
        <loc:MyStackPanel x:Name="aStackPanel">
            <Label Content="Hi there"/>
            <Button Content="Click me"/>
        </loc:MyStackPanel>

        <Button Content="Visual Children" Click="Button_Click"/>
    </StackPanel>

Code-behind is:

        private void Button_Click(object sender, RoutedEventArgs e)
        {
            StringBuilder sbMsg = new StringBuilder();

            sbMsg.Append("Children of MyStackPanel:\n");
            int childCount = aStackPanel.MyVisualChildrenCount;
            for (int i = 0; i < childCount; i++)
            {
                Visual child = aStackPanel.MyGetVisualChild(i);
                sbMsg.AppendFormat(" - {0}\n", child.GetType().ToString());
            }

            MessageBox.Show(sbMsg.ToString());
        }

Results at run-time: