.netsilverlightwindows-phone-7visualtreehelperframeworkelement

FrameworkElement.Parent and VisualtreeHelper.GetParent behaves differently

In a WP7 app, I used FrameworkElement.Parent recursively to determine whether a specific element is inside of another element. But it does not always work correctly. Then I changed my code to use VisualtreeHelper.GetParent method recursively, and it always work correctly(so far as I tested).

So what is the difference of them?

Thanks

Solution

  • Consider ControlA and ControlB where ControlA is a content control meaning it can contain other controls.

    <ControlA>
   <ControlB />
</ControlA>

    Logically the Parent property of the ControlB instance is an instance of ControlA in this case.

    However if you were to look at Template setter of the default style of ControlA you may find complex Xaml containing some visual state management and a hierarchy of Borders and Grids and finally buried in that lot there is a ContentPresenter where the child control will be placed.

    Recursively looping up VisualTreeHelper.Parent will find each element defined in the template from the ContentPresenter up to the "logical" parent element and then beyond.