xamarin-gradient-border.cs

// Add a border and a shadow to layer in Xamarin.iOS.
// View is a UIView subclass.

// Bottom border
var border = new CALayer();
border.Frame = new RectangleF(0, view.Frame.Height, view.Frame.Width, 1);
border.BackgroundColor = UIColor.Black.CGColor;

// Bottom gradient
var gradient = new CAGradientLayer();
gradient.Colors = new CGColor[] {
  UIColor.FromHSBA(0, 0, 0.5f, 0.5f).CGColor,
  UIColor.FromHSBA(0, 0, 1f, 0).CGColor
};
gradient.Frame = new RectangleF(0, view.Frame.Height + 1, view.Frame.Width, 10);

// Add layers
view.Layer.AddSublayer(border);
view.Layer.AddSublayer(gradient);