ASP.NET Login 登录的时候 输入验证码 怎么弄啊？

        <table width="400" border="0" align="center" cellpadding="1" cellspacing="5" style="height:193px">



          <tr>

            <td colspan="2" align="left"><div align="left">用户名 

                <asp:TextBox ID="TxtName" runat="server" Width="129px" CssClass="username"></asp:TextBox> 

                <asp:RequiredFieldValidator ID="f_UserNameX" runat="server" ControlToValidate="TxtName" ErrorMessage="请填写用户名"></asp:RequiredFieldValidator><script language="javascript" type="text/javascript">document.getElementById('TxtName').focus();</script>

            </div></td>

          </tr>

          <tr>

            <td colspan="2" align="left"><div align="left">密　码 

                <asp:TextBox ID="TxtPassword" runat="server"  CssClass="password" TextMode="Password" Width="129px" MaxLength="18"></asp:TextBox> 

                <asp:RequiredFieldValidator ID="f_PasswordX" runat="server" ControlToValidate="TxtPassword" ErrorMessage="请填写密码"></asp:RequiredFieldValidator>

                </div></td>

          </tr>

         <tr runat="server" id="safeCodeVerify_1">

            <td colspan="2" align="left"><div align="left">安全码 

                <asp:TextBox ID="TxtSafeCode" runat="server"  CssClass="password" TextMode="Password" Width="129px" MaxLength="80"></asp:TextBox> 

                <asp:RequiredFieldValidator ID="f_safeCodeVerify" runat="server" ControlToValidate="TxtSafeCode" ErrorMessage="请填写安全码"></asp:RequiredFieldValidator>

                </div></td>

          </tr>

          

          <tr>

            <td style="width:53%;" align="left">效验码 

                <asp:TextBox ID="TxtVerify" CssClass="vercode" runat="server" Width="52px"></asp:TextBox>

                <script type="text/javascript" language="JavaScript">

                   var numkey = Math.random();

                   numkey = Math.round(numkey*10000);

                   document.write("<img src=\"../comm/Image.aspx?k="+ numkey +"\" width=\"70\" onClick=\"this.src+=Math.random()\" alt=\"图片看不清？点击重新得到验证码\" style=\"cursor:pointer;\" height=\"23\" hspace=\"4\"");

                </script>             </td>

          </tr>

          <tr>

            <td colspan="2" align="left" style="height:36px;">

                <asp:HiddenField ID="HidUrl" runat="server" />

                 <asp:ImageButton ID="ImageButton1" runat="server" ImageUrl="../sysImages/Login/signin.gif" OnClick="login_Click" />    

                <label><asp:ImageButton ID="ImageButton2" runat="server" ImageUrl="../sysImages/Login/reset.gif" OnClientClick="javascript:window.close();" /></label></td>

          </tr>

        </table>

        string Account = this.TxtName.Text;

        string PassWord = this.TxtPassword.Text;

        string VerifyCode = this.TxtVerify.Text.Trim();

        string SafeCode = this.TxtSafeCode.Text;

        string Urls = this.HidUrl.Value;

        string SN_SERAL = this.TxtSafeCode.Text;

        if (Account.Trim() == string.Empty || PassWord.Trim() == string.Empty)

        {

            PageError("用户与密码不能为空,详细请查看帮助说明!", "login.aspx?" + Request.QueryString);

        }

        if (Session["CheckCode"] == null)

        {

            PageError("验证码过期，请返回重新登录!", "login.aspx?" + Urls + "");

        }

        string CheckCode = Session["CheckCode"].ToString().ToUpper();

        Session.Remove("CheckCode");

        if (VerifyCode.ToUpper() != CheckCode)

        {

            PageError("输入验证码错误!", "login.aspx?" + Urls + "");

        }

using System;

using System.Collections.Generic;

using System.Text;

using System.Drawing;

using System.Drawing.Imaging;



namespace Galsun.Nfdw.Web.UI

{

    public class ImagePage : System.Web.UI.Page

    {

        /// <summary>

        /// 随机码认证

        /// </summary>

        /// <param name="code">生成认证长度</param>

        protected void DrawImage(int code)

        {

            Session["CheckCode"] = Galsun.Common.Rand.Number(code);

            CreateImages(Session["CheckCode"].ToString());

        }

        /// <summary>

        /// /// 生成验证图片

        /// /// </summary>

        /// /// <param name="checkCode">验证字符</param>

        protected void CreateImages(string checkCode)

        {

            int iwidth = (int)(checkCode.Length * 15);

            System.Drawing.Bitmap image = new System.Drawing.Bitmap(iwidth, 30);

            Graphics g = Graphics.FromImage(image);

            g.Clear(Color.LightCyan);

            //定义颜色

            Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple, Color.SkyBlue };

            //定义字体 

            string[] font = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体", "Comic Sans MS" };

            Random rand = new Random();

            //随机输出噪点

            for (int i = 0; i < 150; i++)

            {

                int x = rand.Next(image.Width);

                int y = rand.Next(image.Height);

                g.DrawPie(new Pen(Color.LightGray, 0), x, y, 6, 6, 1, 1);

            }



            //输出不同字体和颜色的验证码字符

            for (int i = 0; i < checkCode.Length; i++)

            {

                int cindex = rand.Next(7);

                int findex = rand.Next(6);

                Font _font = new System.Drawing.Font(font[findex], 14, System.Drawing.FontStyle.Bold);

                Brush b = new System.Drawing.SolidBrush(c[cindex]);

                int ii = 4;

                if ((i + 1) % 2 == 0)

                {

                    ii = 2;

                }

                g.DrawString(checkCode.Substring(i, 1), _font, b, 3 + (i * 12), ii);

            }



            //画一个边框

            g.DrawRectangle(new Pen(Color.Red, 0), 100, 0, image.Width - 1, image.Height - 1);

            //输出到浏览器

            System.IO.MemoryStream ms = new System.IO.MemoryStream();

            image.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);

            Response.ClearContent();//Response.ClearContent();

            Response.ContentType = "image/Jpeg";

            Response.BinaryWrite(ms.ToArray());

            g.Dispose();

            image.Dispose();

        }

    }

}

public partial class Inc_CheckCode : System.Web.UI.Page

{

    protected void Page_Load(object sender, EventArgs e)

    {

        // 在此处放置用户代码以初始化页面

        this.CreateCheckCodeImage(GenerateCheckCode());

    }



    //产生随机数的函数

    private string GenerateCheckCode()

    {

        int number;

        string checkCode = String.Empty;



        System.Random random = new Random();





        //随机产生一个整数 





        for (int i = 0; i < 4; i++)

        {

            number = random.Next(65,90);

            

            checkCode += Convert.ToChar(number);

        }





            Session["CheckCode"] = checkCode;

        //Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));



        return checkCode;

    }

    //建立一个随机图形

    private void CreateCheckCodeImage(string checkCode)

    {

        if (checkCode == null || checkCode.Trim() == String.Empty)

            return;

        //建立一个位图文件 确立长宽

        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.Silver), x1, y1, x2, y2);

            //				}

            //把产生的随机数以字体的形式写入画面

            Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold | System.Drawing.FontStyle.Italic));

            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<100; 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();

        }

    }



}