postButton.TouchUpInside += delegate {

                Twitpic tp;
                tp = new Twitpic();

                byte[] picture = UIImageToByte (imageView.Image);

                string twitPicURL;
                string user = username.Text;
                string pass = password.Text;

                twitPicURL = tp.UploadPhoto (picture, "PNG", tweet.Text, "monotouch.png" , user, pass);
            };