WinRT/C++ Get parent Page control of the Page inside the Frame

December 15, 2021

Best way to get parent Page control from Page inside Frame on desktop application built with WinRT/C++ UI.

Illustration:

MainPage
    ^^Frame
        ^^SecondPage
            ^^Frame
                ^^ThirdPage
                    ^^Keep going

So, how to get MainPage control from SecondPage or even from ThirdPage onwards.

>Solution :

You can use the VisualTreeHelper to navigate the visual tree. The following implementation goes up the visual tree starting at a root element, and returns an element that matches the requested ancestor_type, or a null com_ptr if there isn’t any that matches:

template <typename ancestor_type>
auto find_ancestor(::winrt::Windows::UI::Xaml::DependencyObject root) noexcept
{
    auto ancestor { root.try_as<ancestor_type>() };
    while (!ancestor && root)
    {
        root = ::winrt::Windows::UI::Xaml::Media::VisualTreeHelper::GetParent(root);
        ancestor = root.try_as<ancestor_type>();
    }
    return ancestor;
}

You can use this to move from Page to Page, skipping over the intermediate Frame‘s until you are at the top of the tree.