Nested ItemsControls' binding breaks when underlying data source changes, and the ItemsControls are collapsed

Question

Windows Phone WinRT App, targeted to Windows Phone 8.1.
I have a nested data structure: class (SampleDataSource), that has an ObservableCollection (Groups) that contains class (SampleDataGroup) items that has an ObservableCollection (Items)
that contains class (SampleDataItem) items.
SampleDataSource is the DataContext of root item, a pivot control's ItemsSource is set to
Groups. In the pivot's DataTemplate there is an ItemsControl with ItemsSource set to
Items.
The above scenario is a slightly modified version of the pivot app template that is generated by Visual Studio.
So far it works properly.
Then I added a ToggleSwitch to the page that toggles the Visibility of the pivot.
Still works.
Then I added some more code to clear the Groups ObservableCollection when the pivot made collapsed, and reload the data before its visibility is set back to visible.
The result is that the top-level ItemsControl (the pivot) gets displayed properly, but the ItemsControl is empty. If I scroll to an other pivot page, the ItemsControl is populated, and from this point everything works correctly, even the initially empty
ItemsControl works just fine.
The code that is relevant to the issue is:
private async void ToggleVisibility_Toggled(object sender, RoutedEventArgs e)
if (pivot != null)
// Was collapsed, therefore we are going to show it, so load the data source
if (pivot.Visibility == Windows.UI.Xaml.Visibility.Collapsed)
await SampleDataSource.GetInstance().GetSampleDataAsync();
pivot.Visibility = (sender as ToggleSwitch).IsOn ? Visibility.Visible : Visibility.Collapsed;
// Just got collapsed, so remove the data from memory
if (pivot.Visibility == Windows.UI.Xaml.Visibility.Collapsed)
SampleDataSource.GetInstance().Groups.Clear();
The project (as mentioned above, it's a slightly modified version of Pivot App template) that reproduces this issue is available
HERE.
Does anyone have any idea what I should do to make ItemsControl work properly after making pivot visible?

Answer 1

I can't help you with this myself as I've not done it but there are quite a few tutorials kicking around the net.
Simple ODBC Connections in Adobe LiveCycle:
http://www.youtube.com/watch?v=C56_Cz-aE0c
Connecting a form to a database:
http://forms.stefcameron.com/2006/09/18/connecting-a-form-to-a-database/
Database connected forms:
http://acrobatusers.com/tutorials/database-connected-forms