namespace jingdong.Verification_code{    public partial class Default : System.Web.UI.Page    {        protected void Page_Load(object sender, EventArgs e)        {            if (Request.QueryString["mathmod"] != null)            {                if (Request.QueryString["mathmod"] == "reg")                {                    string temp = GenerateCheckCode();                    Session["Verification_code"] = temp;                    this.CreateCheckCodeImage(temp);                }                else if (Request.QueryString["mathmod"] == "repwd")                {                    string temp = GenerateCheckCode();                    Session["repwd_Verification_code"] = temp;                    this.CreateCheckCodeImage(temp);                }            }        }        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));            return checkCode;        }        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 < 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.GreenYellow), x1, y1, x2, y2);                }                Font font = new System.Drawing.Font("Verdana", 10, (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                for (int i = 0; i < 80; 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.Red), 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();            }        }    }}

　　用户密码加密实现:

namespace jingdong{    public class Myencrypt : __encrypt__    {        public string GetSha1(string str)        {            return Encryptions(str);        }    }    public class __encrypt__    {        /// 
        /// 加密接口        /// 
        /// 要加密的字符串        /// 
     
      返回加密以后的密文
             public string Encryptions(string str)        {            return encryptions(str);        }        /// 
        /// 加密实现        /// 
        /// 要加密的字符串        /// 
     
      如果加密成功，返回密文；否则返回空
             private string encryptions(string str)        {            if (!String.IsNullOrEmpty(str))            {                return System.Web.Security.FormsAuthentication.HashPasswordForStoringInConfigFile(str, "SHA1").ToLower();            }            else            {                return string.Empty;            }        }    }}