网站验证码

protected void Page_Load(object sender, EventArgs e)
        {
            this.CreateCheckCodeImage(GenerateCheckCode());
        }
        /// <summary>
        /// 生成一个随机的验证码
        /// </summary>
        /// <returns></returns>
        private string GenerateCheckCode()
        {
            int number;
            char code;
            string checkCode = String.Empty;
            System.Random random = new Random();
            for (int i = 0; i < 5; i++)
            {
                number = random.Next();

                if (number % 2 == 0)
                {
                    code = (char)('0' + (char)(number % 10));
                }
                else
                {
                    code = (char)('A' + (char)(number % 26));
                }

                checkCode += code.ToString();
            }
            //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
            //将验证码写入Session
            Session["checkCode"] = checkCode;
            return checkCode;
        }

        /// <summary>
        /// 创建一个验证码图片
        /// </summary>
        /// <param name="checkCode">验证码字符串</param>
        private void CreateCheckCodeImage(string checkCode)
        {
            if (checkCode == null || checkCode.Trim() == String.Empty)
                return;

            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 12.5)), 22);
            Graphics g = Graphics.FromImage(image);

            try
            {
                //生成随机生成器
                Random random = new Random();

                //清空图片背景色
                g.Clear(Color.White);

                //画图片的背景噪音线
                for (int i = 0; i < 15; i++)
                {
                    int x1 = random.Next(image.Width);
                    int x2 = random.Next(image.Width);
                    int y1 = random.Next(image.Height);
                    int y2 = random.Next(image.Height);

                    g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);
                }

                Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Regular | System.Drawing.FontStyle.Italic));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.ForestGreen, Color.DeepSkyBlue, 1.2f, true);
                g.DrawString(checkCode, font, brush, 2, 2);

                //画图片的前景噪音点
                for (int i = 0; i < 60; i++)
                {
                    int x = random.Next(image.Width);
                    int y = random.Next(image.Height);

                    image.SetPixel(x, y, Color.FromArgb(random.Next()));
                }

                //画图片的边框线
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, image.Width - 1, image.Height - 1);

                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());
            }
            finally
            {
                g.Dispose();
                image.Dispose();
            }
        }