public override void ViewDidLoad()
        {
            base.ViewDidLoad ();
            var v1 = new UIView ();
            v1.BackgroundColor = UIColor.Red;
            this.View.AddSubview (v1);
            v1.AlignTopAndLeading ("20", "20", v1.Superview);
            v1.ConstrainWidthAndHeight ("40", "40");

            // Perform any additional setup after loading the view, typically from a nib.
        }