Find children of a user control, in a tab item

Question

I have an issue related to finding children of a user control. The user control resides in a tab item of a tab control

XAML

<TabControl HorizontalAlignment="Left" Height="100" VerticalAlignment="Top" Width="150">
    <TabItem Header="First tab">
        <Grid Background="#FFE5E5E5"/>
    </TabItem>
    <TabItem Header="Tab with stackpanel" x:Name="tabWithStackPanel">
        <StackPanel>
            <TextBox></TextBox>
            <TextBox></TextBox>
            <TextBox></TextBox>
            <TextBox></TextBox>
            <TextBox></TextBox>
            <TextBox></TextBox>
            <TextBox></TextBox>
        </StackPanel>
    </TabItem>
    <TabItem Header="Tab with user control" x:Name="tabWithUserControl">
        <control:UserControl1/>
    </TabItem>
</TabControl>
<Button Height="46" Width="70" Panel.ZIndex="1001" Click="Button_Click">Find</Button>

The method that return the children of a dependency object

public static List<T> FindChildren<T>(DependencyObject parent) where T : DependencyObject
{
    if (parent == null) return null;

    List<T> children = new List<T>();

    int childrenCount = VisualTreeHelper.GetChildrenCount(parent);

    for (int i = 0; i < childrenCount; i++)
    {
        var child = VisualTreeHelper.GetChild(parent, i);
        T childType = child as T;
        if (childType == null)
        {
            children.AddRange(FindChildren<T>(child));
        }
        else
        {
            children.Add((T)child);
        }
    }

    return children;
}

So as you see in XAML the second TabItem contains a StackPanel which contains some TextBoxes. The third TabItem contains a UserControl which also contains TextBoxes.

Now when I click the Find button the event handler should do the following

    var children1 = Util.FindChildren<TextBox>(tabWithStackPanel.GetValue(TabItem.ContentProperty) as StackPanel);
    var children2 = Util.FindChildren<TextBox>(tabWithUserControl.GetValue(TabItem.ContentProperty) as UserControl1);

The issue is that first line returns all the children of the StackPanel panel, but the second line does not return all the children of the UserControl1.

I have to select the "Tab with user control" first in order to get all the children of the UserControl1.

Any clue how to solve the issue?

Answer 1

The non-selected TabItem doesn't exist in the Visual tree, but does exist in the Logical tree.

Replace your calls to VisualTreeHelper with equivalent calls to LogicalTreeHelper