如何删除动画后'；s已完成

我想从目标属性中删除动画，因为我无法在动画后设置属性。

所以，根据上面问题的答案，我必须在动画完成后删除它。但是如何做到？

这是我的代码：

public class GridLengthAnimation : AnimationTimeline {
    static GridLengthAnimation() {
        FromProperty = DependencyProperty.Register("From", typeof(GridLength), typeof(GridLengthAnimation));
        ToProperty = DependencyProperty.Register("To", typeof(GridLength), typeof(GridLengthAnimation));
    }
    public override Type TargetPropertyType {
        get { return typeof(GridLength); }
    }
    protected override Freezable CreateInstanceCore() {
        return new GridLengthAnimation();
    }
    public ContentElement Target { get; set; }
    public static readonly DependencyProperty FromProperty;
    public GridLength From {
        get { return (GridLength) GetValue(FromProperty); }
        set { SetValue(FromProperty, value); }
    }
    public static readonly DependencyProperty ToProperty;
    public GridLength To {
        get { return (GridLength) GetValue(ToProperty); }
        set { SetValue(ToProperty, value); }
    }
    public void BeginAnimation() {
        Target.BeginAnimation(ColumnDefinition.WidthProperty, null);
        Target.BeginAnimation(ColumnDefinition.WidthProperty, this);
    }
    public IEasingFunction EasingFunction { get; set; } = new CubicEase() { EasingMode = EasingMode.EaseInOut };
    public override object GetCurrentValue(object defaultOriginValue, object defaultDestinationValue, AnimationClock animationClock) {
        double fromValue = ((GridLength) GetValue(FromProperty)).Value;
        double toValue = ((GridLength) GetValue(ToProperty)).Value;
        double newValue = 0;
        if ((fromValue > toValue)) {
            newValue = (1 - EasingFunction.Ease(animationClock.CurrentProgress.Value)) * (fromValue - toValue) + toValue;
            return new GridLength(newValue, GridUnitType.Star);
        } else {
            newValue = EasingFunction.Ease(animationClock.CurrentProgress.Value) * (toValue - fromValue) + fromValue;
            return new GridLength(newValue, GridUnitType.Star);
        }
    }
}

为了开始动画，我在MainWindows.xaml.cs文件中这样做：

GridLengthAnimation gridAnim = new GridLengthAnimation() {
    Name = "gridAnim",
    Target = mainGrid.ColumnDefinitions[1],
    Duration = new Duration(TimeSpan.FromMilliseconds(1000))
};
gridAnim.From = new GridLength(1, GridUnitType.Star);
gridAnim.To = new GridLength(0, GridUnitType.Star);
gridAnim.BeginAnimation();

动画完成后，我可以在哪里删除它？

    GridLengthAnimation gridAnim = new GridLengthAnimation() {
            Name = "gridAnim",
            Target = this.MainGrid.ColumnDefinitions[1],
            Duration = new Duration(TimeSpan.FromMilliseconds(1000))
          };
          gridAnim.From = new GridLength(1, GridUnitType.Star);
          gridAnim.To = new GridLength(0, GridUnitType.Star);
//Cleanup on Complete
          gridAnim.Completed += (sender, args) => {
                                                    var xx = sender as AnimationClock;
                                                    (xx.Timeline as GridLengthAnimation).Target = null;
          };
          gridAnim.BeginAnimation();

public void BeginAnimation() {
    Completed += GridLengthAnimation_Completed;
    Target.BeginAnimation(ColumnDefinition.WidthProperty, null);
    Target.BeginAnimation(ColumnDefinition.WidthProperty, this);
}
private void GridLengthAnimation_Completed(object sender, EventArgs e) {
    //unlocks the property
    Target.BeginAnimation(ColumnDefinition.WidthProperty, null);
    //holds the value at the end
    ((ColumnDefinition) Target).Width = new GridLength(((GridLength) GetValue(ToProperty)).Value, GridUnitType.Star);
}