急求解答！~

新建一个网页文件img.aspx
中文验证码using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Text;
using System.Drawing;namespace Ld.WEB
{    public partial class Img : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            Response.Buffer = true;
            Response.ExpiresAbsolute = DateTime.Now.AddDays(-1);
            Response.AddHeader("pragma", "no-cache");
            Response.AddHeader("cache-control", "");
            Response.CacheControl = "no-cache";
            Response.ContentType = "text/plain";
            //获取GB2312编码页（表） 
            Encoding gb = Encoding.GetEncoding("gb2312");            //调用函数产生4个随机中文汉字编码 
            object[] bytes = ChineseCode.CreateRegionCode(4);            //根据汉字编码的字节数组解码出中文汉字 
            string str1 = gb.GetString((byte[])Convert.ChangeType(bytes[0], typeof(byte[])));
            string str2 = gb.GetString((byte[])Convert.ChangeType(bytes[1], typeof(byte[])));
            string str3 = gb.GetString((byte[])Convert.ChangeType(bytes[2], typeof(byte[])));
            string str4 = gb.GetString((byte[])Convert.ChangeType(bytes[3], typeof(byte[])));
            string[] str = new string[] { str1, str2, str3, str4 };            CreateCheckCodeImage(str);            Session["ChineseCode"] = str1 + str2 + str3 + str4;            if (Request.QueryString["refresh"] != null)
            {
                CreateCheckCodeImage(str);
                string aa = Request.QueryString["refresh"].ToString();
            }
            else
            {
                return;
            }
        }
        private void CreateCheckCodeImage(string[] checkCode)
        {
            if (checkCode == null || checkCode.Length <= 0)
                return;            System.Drawing.Bitmap image = new System.Drawing.Bitmap((int)Math.Ceiling((checkCode.Length * 32.5)), 60);
            System.Drawing.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 < 20; 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);
                }                //定义颜色
                Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };
                //定义字体
                string[] f = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "黑体" };                for (int k = 0; k <= checkCode.Length - 1; k++)
                {
                    int cindex = random.Next(7);
                    int findex = random.Next(5);                    Font drawFont = new Font(f[findex], 16, (System.Drawing.FontStyle.Bold));                    SolidBrush drawBrush = new SolidBrush(c[cindex]);                    float x = 5.0F;
                    float y = 0.0F;
                    float width = 20.0F;
                    float height = 25.0F;
                    int sjx = random.Next(10);
                    int sjy = random.Next(image.Height - (int)height);                    RectangleF drawRect = new RectangleF(x + sjx + (k * 25), y + sjy, width, height);                    StringFormat drawFormat = new StringFormat();
                    drawFormat.Alignment = StringAlignment.Center;                    g.DrawString(checkCode[k], drawFont, drawBrush, drawRect, drawFormat);
                }                //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();
            }
        }
    }
}找一个img标签<img scr="img.aspx"/>登陆验证            string code = this.TextBox1.Text;
            if (Session["ChineseCode"] == null)
            {
                //这里写不允许登陆的代码
                return;
            }
            string ChineseCode = Session["ChineseCode"].ToString();
            if (code != ChineseCode)
            {
                //验证码不要对。这里写不允许登陆的代码            }
            else
            {
                 //验证码对。跳转
            }