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;
            }
        }
    }