public static Storyboard FadeIn(this FrameworkElement frameworkElement, FrameworkElement parent, TimeSpan duration, Action completed = null)
        {
            if (parent == null)
                throw new NullReferenceException("parent");
            if (BaseComponent.getCPtr(parent).Handle == IntPtr.Zero)
                throw new NullReferenceException("parent");

            frameworkElement.Opacity = 0;
            string key = "Fade" + frameworkElement.GetHashCode();
            StopStoryboard(key, parent);

            if (parent.Resources.Contains(key))
            {
                UnityEngine.Debug.LogWarning("Resource already exists");
                return null;
            }

            DoubleAnimation animation = new DoubleAnimation();
            animation.Duration = new Duration(duration);
            animation.AutoReverse = false;
            animation.FillBehavior = FillBehavior.Stop;

            Storyboard storyboard = new Storyboard();
            storyboard.AutoReverse = false;
            storyboard.Duration = animation.Duration;
            storyboard.FillBehavior = FillBehavior.Stop;
            storyboard.Children.Add(animation);


            parent.Resources.Add(key, storyboard);

            Storyboard.SetTarget(animation, frameworkElement);
            Storyboard.SetTargetProperty(animation, new PropertyPath("Opacity"));
            animation.From = frameworkElement.Opacity;
            animation.To = 1;
            storyboard.Completed += (sender2, e2) =>
            {
                parent.Resources.Remove(key);
                frameworkElement.Opacity = 1.0f;
                completed?.Invoke();
            };

            storyboard.Begin();
            return storyboard;
        }