Windowstemplatestudio: Nested NavigationViewItem.MenuItems Aren't Found OnItemInvoked

[myokeeh]

Describe the bug
With the release of WinUI 2.4, this code fails to find NavigationViewItem.MenuItems nested under NavigationViewItems.

ShellViewModel.cs:

        private void OnItemInvoked(WinUI.NavigationViewItemInvokedEventArgs args)
        {
            if (args.IsSettingsInvoked)
            {
                NavigationService.Navigate(typeof(SettingsViewModel).FullName);
                return;
            }
            if (_navigationView is WinUI.NavigationView)
            {
                //this line below fails to find the activated MenuItem
                var item = _navigationView.MenuItems
                                .OfType<WinUI.NavigationViewItem>()
                                .First(menuItem => (string)menuItem.Content == (string)args.InvokedItem);

                if (item.GetValue(NavHelper.NavigateToProperty) is string pageKey)
                {
                    NavigationService.Navigate(pageKey);
                }

            }
        }

[sibille]

Thanks for reporting!

[mvegaca]

You can fix this Issue with some code modifications in ShellViewModel

Add this GetSelectedItem method:

private WinUI.NavigationViewItem GetSelectedItem(IEnumerable<object> menuItems, Func<WinUI.NavigationViewItem, bool> predicate)
{
    foreach (var item in menuItems.OfType<WinUI.NavigationViewItem>())
    {
        if (predicate(item))
        {
            return item;
        }
        else if (item.MenuItems.Any())
        {
            var selectedChild = GetSelectedItem(item.MenuItems, predicate);
            if (selectedChild != null)
            {
                return selectedChild;
            }
        }
    }

    return null;
}

Update the OnItemInvoked method:

private void OnItemInvoked(WinUI.NavigationViewItemInvokedEventArgs args)
{
    if (args.IsSettingsInvoked)
    {
        NavigationService.Navigate(typeof(SettingsPage));
        return;
    }
    //REMOVE THAT CODE
    //var item = _navigationView.MenuItems
    //                .OfType<WinUI.NavigationViewItem>()
    //                .First(menuItem => (string)menuItem.Content == (string)args.InvokedItem);
    //var pageType = item.GetValue(NavHelper.NavigateToProperty) as Type;
    //NavigationService.Navigate(pageType);

    // ADD THAT CODE
    var selectedItem = GetSelectedItem(_navigationView.MenuItems, item => (string)item.Content == (string)args.InvokedItem);
    if (selectedItem != null)
    {
        var pageType = selectedItem.GetValue(NavHelper.NavigateToProperty) as Type;
        NavigationService.Navigate(pageType);
    }
}

Update the Frame_Navigated method:

private void Frame_Navigated(object sender, NavigationEventArgs e)
{
    IsBackEnabled = NavigationService.CanGoBack;
    if (e.SourcePageType == typeof(SettingsPage))
    {
        Selected = _navigationView.SettingsItem as WinUI.NavigationViewItem;
        return;
    }
    // REMOVE THAT CODE
    //Selected = _navigationView.MenuItems
    //                .OfType<WinUI.NavigationViewItem>()
    //                .FirstOrDefault(menuItem => IsMenuItemForPageType(menuItem, e.SourcePageType));

    // ADD THAT CODE
    var selected = GetSelectedItem(_navigationView.MenuItems, item => IsMenuItemForPageType(item, e.SourcePageType));
    if (selected != null)
    {
        Selected = selected;
    }
}

Thank you for reporting the issue we will include this change when we'll update to WinUI 2.4.

Here is an App with these updates.

Issue3657ReproApp.zip

[myokeeh]

For my reference, which template needs to change? I was trying to look for it, but couldn't find where to make the change.

[mvegaca]

I've found an easier way to solve this, I'll update the templates today so you can see in pull request which templates are affected.

private void OnItemInvoked(WinUI.NavigationViewItemInvokedEventArgs args)
{
    if (args.IsSettingsInvoked)
    {
        NavigationService.Navigate(typeof(SettingsPage), null, args.RecommendedNavigationTransitionInfo);
        return;
    }

    if (args.InvokedItemContainer is WinUI.NavigationViewItem selectedItem)
    {
        var pageType = selectedItem.GetValue(NavHelper.NavigateToProperty) as Type;
        NavigationService.Navigate(pageType, null, args.RecommendedNavigationTransitionInfo);
    }
}

private void Frame_Navigated(object sender, NavigationEventArgs e)
{
    IsBackEnabled = NavigationService.CanGoBack;
    if (e.SourcePageType == typeof(SettingsPage))
    {
        Selected = _navigationView.SettingsItem as WinUI.NavigationViewItem;
        return;
    }

    var selectedItem = GetSelectedItem(_navigationView.MenuItems, e.SourcePageType);
    if (selectedItem != null)
    {
        Selected = selectedItem;
    }
}

private WinUI.NavigationViewItem GetSelectedItem(IEnumerable<object> menuItems, Type pageType)
{
    foreach (var item in menuItems.OfType<WinUI.NavigationViewItem>())
    {
        if (IsMenuItemForPageType(item, pageType))
        {
            return item;
        }

        var selectedChild = GetSelectedItem(item.MenuItems, pageType);
        if (selectedChild != null)
        {
            return selectedChild;
        }
    }

    return null;
}

[myokeeh]

@mvegaca, I just copied over the code above, but it's not quite working for me. Is this for the MvvmLight version? The NavigationService.Navigate() don't take the same arguments. I haven't put all my effort into it yet, and will look at it again in the morning.

Edit: I see how it needs to look like for MvvmLight in the pull request. Thanks!

[sibille]

Verified in dev-nightly:
Templates version: 0.22.20150.1
Wizard version: 0.22.20150.1