Create QR code

gistfile1.cs

var imageView = new UIImageView ();
imageView.Frame = UIScreen.MainScreen.Bounds;
imageView.ContentMode = UIViewContentMode.ScaleAspectFit;

var qrCode = new CIQRCodeGenerator {
    Message = NSData.FromString ("test"),
    CorrectionLevel = "Q"
}.OutputImage;

UIGraphics.BeginImageContext (new SizeF (qrCode.Extent.Width * 8, qrCode.Extent.Height * 8));
var cgCtx = UIGraphics.GetCurrentContext ();
var ciCtx = CIContext.FromOptions (null);
cgCtx.InterpolationQuality = CGInterpolationQuality.None;
cgCtx.DrawImage (cgCtx.GetClipBoundingBox (), ciCtx.CreateCGImage (qrCode, qrCode.Extent));
using (var image = UIGraphics.GetImageFromCurrentImageContext ()) {
    imageView.Image = image;
}
UIGraphics.EndImageContext ();
View.AddSubview (imageView);