验证码(一)

别忘了加命名空间啊 using System.Drawing;

protected void Page_Load(object sender, EventArgs e)
        {
            CreateImage(ImageCode());

        }

        private string ImageCode()
        {
            //创建整型型变量
            int number;
            //创建字符型变量
            char code;
            //创建字符串变量并初始化为空
            string checkCode = String.Empty;
            //创建Random对象
            Random random = new Random();
            //使用For循环生成4个数字
            for (int i = 0; i < 4; i++)
            {
                //生成一个随机数
                number = random.Next();
                //将数字转换成为字符型
                code = (char)('0' + (char)(number % 10));

                checkCode += code.ToString();
            }
            //将生成的随机数添加到Cookies中
            Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));
            //返回字符串
            return checkCode;
        }
        private void CreateImage(string Image)
        {
            //判断字符串是否为空
            if (Image == null || Image.Trim() == string.Empty)
            {
                return;
            }
            //创建一个图位对象
            System.Drawing.Bitmap img = new System.Drawing.Bitmap((int)Math.Ceiling((Image.Length * 12.5)), 22);
            //创建Graphics对象
            Graphics g = Graphics.FromImage(img);

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

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

                //画图片背景噪音线
                for (int i = 0; i < 2; i++)
                {
                    int x1 = random.Next(img.Width);
                    int x2 = random.Next(img.Width);
                    int y1 = random.Next(img.Height);
                    int y2 = random.Next(img.Height);

                    g.DrawLine(new Pen(Color.Black), x1, x2, y1, y2);
                }
                Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));
                System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, img.Width, img.Height), Color.Blue, Color.DarkRed, 1.2f, true);
                g.DrawString(Image, font, brush, 2, 2);

                //画图片的前景噪音点
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(img.Width);
                    int y = random.Next(img.Height);

                    img.SetPixel(x, y, Color.FromArgb(random.Next()));
                }
                //画图片的边框
                g.DrawRectangle(new Pen(Color.Silver), 0, 0, img.Width - 1, img.Height - 1);

                //将图片输出到页面上
                System.IO.MemoryStream ms = new System.IO.MemoryStream();
                img.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);
                Response.ClearContent();
                Response.ContentType = "image/Gif";
                Response.BinaryWrite(ms.ToArray());

            }
            finally
            {
                g.Dispose();
                img.Dispose();
            }

        }