调试易

定义一个数组string[] chars = {"0", "1", ..."Z"};string rndNumber = "";
for (int i=0; i<8; i++)
{
rndNumber += chars[(new Random).Next(chars.Length)];
}

//获得x位随机字符串
        public static string GetRandomString(int length)
        {
            string str="q,w,e,r,t,y,u,i,o,p,a,s,d,f,g,h,j,k,l,m,n,b,v,c,x,z,1,2,3,4,5,6,7,8,9,0"; 
            
            string [] s=str.Split(",".ToCharArray());             string t="";            Random rm = new Random();            for (int i=0;i<length;i++)
            {
                t += s[rm.Next(0, 35)];
            }            return t;
        }

string[] chars = {"0", "1", ..."Z"};    
DateTime dt = new DateTime();
dt = DateTime.Now;
Random rnd = new Random(dt.Millisecond);
                        string rndNumber = ""; 
for (int i=0; i<8; i++)
{
rndNumber += chars[rnd.Next(chars.Length)];
}

  #region//生验证码随即数字+字母组合
    private string RndNum(int VcodeNum)
    {
        string Vchar = "a,b,c,d,e,0,1,2,3,4,5,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,0,1,2,3,4,5,6,7,8,9,w,x,y,z,a,b,c,d,e,f,g,h,i,j,k,l,m,1,2,3,4,5,6,7,8,9,n,o,p,q,r,s,t,u,v,w,x,y,z";
        string[] VcArray = Vchar.Split(new Char[] { ',' });
        string VNum = "";
        int temp = -1;        Random rand = new Random();        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
            }            int t = rand.Next(35);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);
            }
            temp = t;
            VNum += VcArray[t];
        }
        return VNum;
    }
    #endregion

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.Drawing.Imaging;
using System.Drawing;
using System.IO;
public partial class include_ValidateCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string tmp = RndNum(5).ToUpper();
        this.Session["ImageV"] = tmp;
        HttpCookie a = new HttpCookie("ImageV", tmp);
        Response.Cookies.Add(a);
        this.CreateCheckCodeImage(tmp);
    }
    #region//创建验证码
    private void ValidateCode(string VNum)
    {
        Bitmap Img = null;
        Graphics g = null;
        MemoryStream ms = null;        int gheight = VNum.Length * 10;
        Img = new Bitmap(gheight, 25);
        g = Graphics.FromImage(Img);
        //背景颜色 
        g.Clear(Color.White);
        //文字字体 
        Font f = new Font("Arial Black", 10);
        //文字颜色 
        SolidBrush s = new SolidBrush(Color.Black);
        g.DrawString(VNum, f, s, 3, 3);
        ms = new MemoryStream();
        Img.Save(ms, ImageFormat.Jpeg);
        Response.ClearContent();
        Response.ContentType = "image/Jpeg";
        Response.BinaryWrite(ms.ToArray());        g.Dispose();
        Img.Dispose();
        Response.End();
    }
    #endregion
    #region//生验证码随即数字+字母组合
    private string RndNum(int VcodeNum)
    {
        string Vchar = "a,b,c,d,e,0,1,2,3,4,5,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,0,1,2,3,4,5,6,7,8,9,w,x,y,z,a,b,c,d,e,f,g,h,i,j,k,l,m,1,2,3,4,5,6,7,8,9,n,o,p,q,r,s,t,u,v,w,x,y,z";
        string[] VcArray = Vchar.Split(new Char[] { ',' });
        string VNum = "";
        int temp = -1;        Random rand = new Random();        for (int i = 1; i < VcodeNum + 1; i++)
        {
            if (temp != -1)
            {
                rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));
            }            int t = rand.Next(35);
            if (temp != -1 && temp == t)
            {
                return RndNum(VcodeNum);
            }
            temp = t;
            VNum += VcArray[t];
        }
        return VNum;
    }
    #endregion
    #region //创建验证码背景图片
    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 * 13.0)), 21);
        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);
            }            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, 1);            //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();
        }
    }
    #endregion
}这个是生成5位的。生成8位的自己改改