验证码

/// <summary>

    /// 生成验证码代码

    /// </summary>

    public class WaterMark : IHttpHandler,IRequiresSessionState //要使用session必须实现该接口,记得要导入System.Web.SessionState命名空间

    {



        public void ProcessRequest(HttpContext context)

        {

            string checkCode = GenCode(5);  // 产生5位随机字符

            context.Session["Code"] = checkCode; //将字符串保存到Session中，以便需要时进行验证

            using (Bitmap image = new Bitmap(70, 22))

            {

                using (Graphics g = Graphics.FromImage(image))

                {

                    //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

                    int i;

                    for (i = 0; i < 25; 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.Bold));

                    System.Drawing.Drawing2D.LinearGradientBrush brush = new System.Drawing.Drawing2D.LinearGradientBrush(new Rectangle(0, 0, image.Width, image.Height), Color.Blue, Color.DarkRed, 1.2F, true);

                    g.DrawString(checkCode, font, brush, 2, 2);



                    //画图片的前景噪音点

                    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);

                    context.Response.ClearContent();

                    context.Response.ContentType = "image/Gif";

                    context.Response.BinaryWrite(ms.ToArray());

                }

            }

        }



        /// <summary>

        /// 产生随机字符串

        /// </summary>

        /// <param name="num">随机出几个字符</param>

        /// <returns>随机出的字符串</returns>

        private string GenCode(int num)

        {

            string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";

            char[] chastr = str.ToCharArray();

            string code = "";

            Random rd = new Random();

            int i;

            for (i = 0; i < num; i++)

            {

                code += str.Substring(rd.Next(0, str.Length), 1);

            }

            return code;



        }



        public bool IsReusable

        {

            get

            {

                return false;

            }

        }

    }