Eu tenho um Canvas com alguns UIElements. Depois de movê-los para a tela animando as propriedades superior e esquerda, muito ocasionalmente uma chamada subseqüente ao Canvas.GetTop resulta em NaN.

Não estou 'fechando' as animações corretament

Veja como estou fazendo a jogada

private void InternalMove(double durationMS, FrameworkElement fElement, Point point, EventHandler callback)
{
   _moveElement = fElement;
   _destination = point;

   Duration duration = new Duration(TimeSpan.FromMilliseconds(durationMS));

   DoubleAnimation moveLeftAnimation = new DoubleAnimation(Canvas.GetLeft(fElement), point.X, duration, FillBehavior.Stop);
   Storyboard.SetTargetProperty(moveLeftAnimation, new PropertyPath("(Canvas.Left)"));

   DoubleAnimation moveTopAnimation = new DoubleAnimation(Canvas.GetTop(fElement), point.Y, duration, FillBehavior.Stop);
   Storyboard.SetTargetProperty(moveTopAnimation, new PropertyPath("(Canvas.Top)"));

   // Create a storyboard to contain the animation.
   _moveStoryboard = new Storyboard();
   if (callback != null) _moveStoryboard.Completed += callback;

   _moveStoryboard.Completed += new EventHandler(s1_Completed);
   _moveStoryboard.Children.Add(moveLeftAnimation);
   _moveStoryboard.Children.Add(moveTopAnimation);
   _moveStoryboard.FillBehavior = FillBehavior.Stop;
   _moveStoryboard.Begin(fElement);
}

private void s1_Completed(object sender, EventArgs e)
{
    if (_moveStoryboard != null)
    {
       _moveStoryboard.BeginAnimation(Canvas.LeftProperty, null, HandoffBehavior.Compose);
       _moveStoryboard.BeginAnimation(Canvas.TopProperty, null, HandoffBehavior.Compose);
    }

    Canvas.SetLeft(_moveElement, _destination.X);
    Canvas.SetTop(_moveElement, _destination.Y);
}

obrigad