UWP app矩形旋转

Question

我创建了一个Rectangle（敌人）。这个矩形射了一颗子弹。当子弹达到窗口边缘时，设置子弹可见性折叠。矩形旋转90度后，但我得到一个错误。为什么不旋转？

我从这个错误中截取了一个屏幕截图：

Enemy.cs

public void rotateEnemy(Rectangle enemy)
{
    RotateTransform transform = new RotateTransform()
    {
        CenterX = 0.5,
        CenterY = 0.5,
        Angle = 90,
    };


    enemy.RenderTransformOrigin = new Point(0.5, 0.5);
    enemy.RenderTransform = transform;

    Storyboard storyboard = new Storyboard();

    DoubleAnimation rotate = new DoubleAnimation();
    rotate.From = 0;
    rotate.To = 90;
    rotate.Duration = new Duration(TimeSpan.FromSeconds(2));
    rotate.AutoReverse = false;
    rotate.SetValue(Storyboard.TargetNameProperty, bullet.Name);

    Storyboard.SetTarget(rotate, bullet);
    Storyboard.SetTargetProperty(rotate, "(UIElement.RenderTransform).(RotateTransform.Angle)"));

    storyboard.Children.Add(rotate);
    storyboard.Begin();
}