UWP - Element is already the child of another element.

[spaddlewit]

I created a repro project, based on your existing Mapsui.Forms.Samples PCL project, just drop it in as a replacement:
http://www.spaddlewit.com/UWPError.zip

The issue is when you Navigation.PushAsync or Navigation.PushModalAsync another form on top, and then pop back to the forms with the Mapsui control:

"System.Runtime.InteropServices.COMException: No installed components were detected.\r\n\r\nElement is already the child of another element.\r\n at System.Runtime.InteropServices.WindowsRuntime.IVector`1.Append(T value)\r\n at System.Runtime.InteropServices.WindowsRuntime.VectorToCollectionAdapter.Add[T](T item)\r\n at Mapsui.UI.Uwp.MapControl.InitAnimation()\r\n at Mapsui.UI.Uwp.MapControl.MapControlLoaded(Object sender, RoutedEventArgs e)"

Any idea what's going on here?

[spaddlewit]

Here's the fix, in Mapsui.UI.Uwp.MapControl.InitAnimation():

Check if the children collection already contains '_zoomAnimation' before adding it.

        if (!_zoomStoryBoard.Children.Contains(_zoomAnimation))
            _zoomStoryBoard.Children.Add(_zoomAnimation);

[spaddlewit]

This might also not be the completely 'correct' fix... should MapControlLoaded be allowed to potentially fire multiple times? Or should the event be removed inside of the MapControlLoaded event callback?