[WPF] 动画Completed事件里获取执行该动画的UI对象

DoubleAnimation ani = new DoubleAnimation();
ani.From = start;
ani.To = end;
ani.Duration = new Duration(TimeSpan.FromSeconds(0.25));
ani.Completed += ani_Completed;

/* !!! 附加属性Storyboard.Target，用于指定执行动画的UI对象 !!! */
Storyboard.SetTarget(ani, uiElement);

 /* 启动动画 */
uiElement.BeginAnimation(Canvas.LeftProperty, ani);

if (sender is AnimationClock)
{
　　AnimationTimeline timeline = (sender as AnimationClock).Timeline;
   /* !!! 通过附加属性把UI对象取回 !!! */
   object uiElement = Storyboard.GetTarget(timeline);
}