表示动画的缓动函数。
 public override void AddKayFrameToAnimation(KeyFrameAnimation animation)
 {
     if (animation is Vector4KeyFrameAnimation)
     {
         (animation as Vector4KeyFrameAnimation).InsertKeyFrame((float)Progress, ValueObject, EasingFunction.CreateCompositionEasingFunction(animation.Compositor));
     }
     else
     {
         throw new InvalidOperationException("错误的动画类型。");
     }
 }
 public override void AddKayFrameToAnimation(KeyFrameAnimation animation)
 {
     animation.InsertExpressionKeyFrame((float)Progress, Expression, EasingFunction.CreateCompositionEasingFunction(animation.Compositor));
 }