这段代码绘制了一个三角形，但应该给你基本的想法。 对于iOS和Mac，CoreGraphics API应该是相同的，因此一个示例应该很容易转换为另一个：

using CoreGraphics;

public class CustomDrawnView : NSView
{
        private const bool useBezeirPath = true;

        // Called when created from unmanaged code
        public CustomDrawnView(IntPtr handle) : base(handle)
        {
            Initialize();
        }

        // Called when created directly from a XIB file
        [Export("initWithCoder:")]
        public CustomDrawnView(NSCoder coder) : base(coder)
        {
            Initialize();
        }

        public CustomDrawnView(CGRect rect): base(rect)
        {

        }

        // Shared initialization code
        void Initialize()
        {

        }
        
        public override void DrawRect(CGRect dirtyRect)
        {
            if(useBezeirPath)
            {
                NSColor.Red.Set();
                NSBezierPath.StrokeLine(new CGPoint(10,10), new CGPoint(100,100));
            }
            else
            {
                var context = NSGraphicsContext.CurrentContext.CGContext;
                context.SetStrokeColor(NSColor.Black.CGColor);
                context.SetLineWidth(1);
                
                var rectangleCGPath = CGPath.FromRoundedRect(new CGRect(10,10,100,100), 4, 4);
                
                context.AddPath(rectangleCGPath);
                context.StrokePath();
            }
        }
}
var mainView = new CustomDrawnView(MainWindow.ContentView.Frame);

MainWindow.ContentView = mainView;