protected override void AnimationFinish(object sender, AnimationFinishEventArgs e)
 {
     PopState();
 }
 protected override void AnimationFinish(object sender, AnimationFinishEventArgs e)
 {
     throw new NotImplementedException();
 }
 protected abstract void AnimationFinish(object sender, AnimationFinishEventArgs e);
 private void OnFinish(AnimationFinishEventArgs e)
 {
     if (Finish != null)
         Finish(this, e);
 }