WPF: Spalten eines Grid-Elementes animieren

public class GridLengthAnimation : AnimationTimeline

{

    public override Type TargetPropertyType

    {

        get { return typeof(GridLength); }

    }

    protected override System.Windows.Freezable CreateInstanceCore()

    {

        return new GridLengthAnimation();

    }

    public static readonly DependencyProperty FromProperty = 

        DependencyProperty.Register("From", typeof(GridLength), typeof(GridLengthAnimation));

    public GridLength From

    {

        get

        {

            return (GridLength)GetValue(GridLengthAnimation.FromProperty);

        }

        set

        {

            SetValue(GridLengthAnimation.FromProperty, value);

        }

    }

    private double FromAsDouble

    {

        get

        {

            return ((GridLength)From).Value;

        }

    }

    public static readonly DependencyProperty ToProperty = 

        DependencyProperty.Register("To", typeof(GridLength), typeof(GridLengthAnimation));

    public GridLength To

    {

        get

        {

            return (GridLength)GetValue(GridLengthAnimation.ToProperty);

        }

        set

        {

            SetValue(GridLengthAnimation.ToProperty, value);

        }

    }

    private double ToAsDouble

    {

        get

        {

            return ((GridLength)To).Value;

        }

    }

    public GridUnitType GridUnitType

    {

        get { return (GridUnitType)GetValue(GridUnitTypeProperty); }

        set { SetValue(GridUnitTypeProperty, value); }

    }

    public static readonly DependencyProperty GridUnitTypeProperty =

        DependencyProperty.Register("GridUnitType", typeof(GridUnitType), typeof(GridLengthAnimation), new UIPropertyMetadata(GridUnitType.Pixel));

    public override object GetCurrentValue(object defaultOriginValue, 

                                            object defaultDestinationValue, 

                                            AnimationClock animationClock)

    {

        if (FromAsDouble > ToAsDouble)

            return new GridLength((1 - animationClock.CurrentProgress.Value) *

                (FromAsDouble - ToAsDouble) + ToAsDouble, this.GridUnitType);

        return new GridLength(animationClock.CurrentProgress.Value *

            (ToAsDouble - FromAsDouble) + FromAsDouble, this.GridUnitType);

    }

}

private void AnimateDetailPane(double from, double to, FrameworkElement element)

{

    GridLengthAnimation gridLengthAnim = new GridLengthAnimation();

    gridLengthAnim.GridUnitType = GridUnitType.Pixel;

    gridLengthAnim.From = new GridLength(from);

    gridLengthAnim.To = new GridLength(to);

    gridLengthAnim.Duration = new Duration(new TimeSpan(0, 0, 0, 0, 300));

    Storyboard.SetTargetName(gridLengthAnim, element.Name);

    Storyboard.SetTargetProperty(gridLengthAnim, new PropertyPath("Width"));

    Storyboard board = new Storyboard();

    board.Children.Add(gridLengthAnim);

    board.Begin(this);

}