GradientColorStackRenderer.cs

using CoreAnimation;  
using CoreGraphics;  
using GadientColorDemo.CustomControls;  
using GadientColorDemo.iOS;  
using Xamarin.Forms;  
using Xamarin.Forms.Platform.iOS;  
[assembly: ExportRenderer(typeof(GradientColorStack), typeof(GradientColorStackRenderer))]  
namespace GadientColorDemo.iOS {  
    public class GradientColorStackRenderer: VisualElementRenderer <StackLayout> {  
        public override void Draw(CGRect rect) {  
            base.Draw(rect);  
            GradientColorStack stack = (GradientColorStack)this.Element;  
            CGColor startColor = stack.StartColor.ToCGColor();  
            CGColor endColor = stack.EndColor.ToCGColor();  
            #region for Vertical Gradient  
            //var gradientLayer = new CAGradientLayer();     
            # endregion
            # region for Horizontal Gradient  
            var gradientLayer = new CAGradientLayer() {  
                StartPoint = new CGPoint(0, 0.5),  
                EndPoint = new CGPoint(1, 0.5)  
            };  
            #endregion  
            gradientLayer.Frame = rect;  
            gradientLayer.Colors = new CGColor[] {  
                startColor,  
                endColor  
            };  
            NativeView.Layer.InsertSublayer(gradientLayer, 0);  
        }  
    }  
}