Find control in the visual tree - wpf

Question

I am trying to get my SelectedRadioButton from a DataTemplate.
Wpf Inspector showed the Visual Tree:
and in code:
void menu_StatusGeneratorChanged(object sender, EventArgs e)
{
var status = Menu.Items.ItemContainerGenerator.Status;
if (status == System.Windows.Controls.Primitives.GeneratorStatus.ContainersGenerated)
{
var item = Menu.Items.ItemContainerGenerator.ContainerFromIndex(0);
// item is a ContentPresenter
var control = Tools.FindChild<SelectedRadioButton>(item);
control = Tools.FindAncestor<SelectedRadioButton>(item);
}
}
item is a ContentPresenter, see the image of Wpf inspector, I believe from there I must be able to get to the SelectedRadioButton. The variable control is always null.
What am I missing here? I use these visualtreehelpers.

Answer 1

The code that I used to traverse the Visual Tree did not use the ApplyTemplate() method for a FrameworkElement in the tree and therefore cildren could not be found. In my situation the following code works:
/// <summary>
/// Looks for a child control within a parent by name
/// </summary>
public static DependencyObject FindChild(DependencyObject parent, string name)
{
// confirm parent and name are valid.
if (parent == null || string.IsNullOrEmpty(name)) return null;
if (parent is FrameworkElement && (parent as FrameworkElement).Name == name) return parent;
DependencyObject result = null;
if (parent is FrameworkElement) (parent as FrameworkElement).ApplyTemplate();
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
result = FindChild(child, name);
if (result != null) break;
}
return result;
}
/// <summary>
/// Looks for a child control within a parent by type
/// </summary>
public static T FindChild<T>(DependencyObject parent)
where T : DependencyObject
{
// confirm parent is valid.
if (parent == null) return null;
if (parent is T) return parent as T;
DependencyObject foundChild = null;
if (parent is FrameworkElement) (parent as FrameworkElement).ApplyTemplate();
int childrenCount = VisualTreeHelper.GetChildrenCount(parent);
for (int i = 0; i < childrenCount; i++)
{
var child = VisualTreeHelper.GetChild(parent, i);
foundChild = FindChild<T>(child);
if (foundChild != null) break;
}
return foundChild as T;
}
Thanks for the comments of "dev hedgehog" for pointing that out (I missed it).
I will not use this approach in production code, it has to be done with databinding like "HighCore" commented.