如何使用xamarin.ios创建圆形脉冲动画？

using CoreAnimation;
using CoreGraphics;
using UIKit;

public class PulseView : UIView
{
    public override void Draw(CGRect rect)
    {
        base.Draw(rect);

        using (var context = UIGraphics.GetCurrentContext())
        {
            var circleRect = new CGRect(rect.X, rect.Y, rect.Width, rect.Height);
            var circlePath = UIBezierPath.FromOval(circleRect);

            context.SetFillColor(UIColor.Clear.CGColor);
            context.SetStrokeColor(UIColor.Red.CGColor);
            context.SetLineWidth(2);

            circlePath.Stroke();
        }
    }

    public void StartPulseAnimation()
    {
        var pulseAnimation = CABasicAnimation.FromKeyPath("transform.scale");
        pulseAnimation.Duration = 1.0;
        pulseAnimation.From = NSNumber.FromFloat(0.0f);
        pulseAnimation.To = NSNumber.FromFloat(1.5f);
        pulseAnimation.TimingFunction = CAMediaTimingFunction.FromName(CAMediaTimingFunction.EaseInEaseOut);
        pulseAnimation.RepeatCount = float.PositiveInfinity;
        pulseAnimation.AutoReverses = true;

        Layer.AddAnimation(pulseAnimation, "pulseAnimation");
    }

    public void StopPulseAnimation()
    {
        Layer.RemoveAnimation("pulseAnimation");
    }
}

public partial class ViewController : UIViewController
{
    private PulseView pulseView;

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        pulseView = new PulseView();
        pulseView.Frame = new CGRect(100, 100, 100, 100);
        View.AddSubview(pulseView);
    }

    public override void ViewDidAppear(bool animated)
    {
        base.ViewDidAppear(animated);

        pulseView.StartPulseAnimation();
    }

    public override void ViewWillDisappear(bool animated)
    {
        base.ViewWillDisappear(animated);

        pulseView.StopPulseAnimation();
    }
}