在登陆时加上验证码

Question

在登陆时加上验证码

Answer 1

使用vs.net2005 自带的验证控件，直接查看vs的帮助系统，查找“验证控件”即可。
其中包括正则表达式验证，用户自己定义的验证准则等。

Answer 2

新建个CheckCode.aspx页：
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;public partial class CheckCode : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        string tmp = GenerateCheckCode();
        Session["CheckCode"] = tmp;
        this.CreateCheckCodeImage(tmp);
    }
    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.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, 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();
        }
    }}
在需要验证码的页面用个image控件，src指向CheckCode.aspx.后台判断Session["CheckCode"] 与输入框

Answer 3

string st1,st2,st3,st4;
st1=random.next(0,9).Tostring();
st2=random.next(0,9).Tostring();
st3=random.next(0,9).Tostring();
st4=random.next(0,9).Tostring();
lable.Text=st1+st2+st3+st4;