验证码

最新推荐文章于 2025-02-27 12:08:26 发布

strangerDemon

最新推荐文章于 2025-02-27 12:08:26 发布

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分类专栏： C# 文章标签：验证码

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本文介绍了一种基于ASP.NET的验证码生成方法，包括验证码图片的动态生成及前端刷新机制。通过随机选择字符、颜色和字体，确保了验证码的不可预测性。此外，还实现了验证码图片的流式传输，确保了用户体验。

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登录时的校验码

//验证码的刷新

$("#image").attr("src", "checkCode.aspx?t=" + (new Date()).getTime());

//验证码的实现

//程序以数据流的形式将后台动态生成的图片数据传到前台，实际并不生成图片

<span style="font-size:18px;">using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Text;
using System.Net;
using System.Drawing;
using System.IO;
using System.Drawing.Imaging;
public partial class admin_checkCode : System.Web.UI.Page
{


protected void Page_Load(object sender, EventArgs e)
    {
        #region 验证码生成
        /// <summary>
        /// 每次加载login.aspx时重新生成一个checkCode
        /// </summary>

        string chkCode = string.Empty;
        //颜色列表，用于验证码、噪线、噪点 
        Color[] color = { Color.Black, Color.Red, Color.Blue, Color.Green, Color.Orange, Color.Brown, Color.Brown, Color.DarkBlue };
        //字体列表，用于验证码 
        string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU", "Impact" };
        //验证码的字符集，去掉了一些容易混淆的字符 
        char[] character = { '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'R', 'S', 'T', 'W', 'X', 'Y' };
        Random rnd = new Random();
        //生成验证码字符串 
        for (int i = 0; i < 4; i++)
        {
            chkCode += character[rnd.Next(character.Length)];
        }
        Bitmap bmp = new Bitmap(100, 40);
        Graphics g = Graphics.FromImage(bmp);
        g.Clear(Color.White);
        //画噪线 
        for (int i = 0; i < 10; i++)
        {
            int x1 = rnd.Next(100);
            int y1 = rnd.Next(40);
            int x2 = rnd.Next(100);
            int y2 = rnd.Next(40);
            Color clr = color[rnd.Next(color.Length)];
            g.DrawLine(new Pen(clr), x1, y1, x2, y2);
        }
        //画验证码字符串 
        for (int i = 0; i < chkCode.Length; i++)
        {
            string fnt = font[rnd.Next(font.Length)];
            Font ft = new Font(fnt, 18);
            Color clr = color[rnd.Next(color.Length)];
            g.DrawString(chkCode[i].ToString(), ft, new SolidBrush(clr), (float)i * 20 + 8, (float)8);
        }
        //画噪点 
        for (int i = 0; i < 100; i++)
        {
            int x = rnd.Next(bmp.Width);
            int y = rnd.Next(bmp.Height);
            Color clr = color[rnd.Next(color.Length)];
            bmp.SetPixel(x, y, clr);
        }
        //清除该页输出缓存，设置该页无缓存 
        Response.Buffer = true;
        Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
        Response.Expires = 0;
        Response.CacheControl = "no-cache";
        Response.AppendHeader("Pragma", "No-Cache");
        //将验证码图片写入内存流，并将其以 "image/Png" 格式输出 
        MemoryStream ms = new MemoryStream();
        try
        {
            bmp.Save(ms, ImageFormat.Png);
            Response.ClearContent();
            Response.ContentType = "image/Png";
            Response.BinaryWrite(ms.GetBuffer());
        }
        finally
        {
            //显式释放资源 
            bmp.Dispose();
            g.Dispose();
        }
        Session["chkCode"] = chkCode;
        Response.End();
    
        #endregion

    }

}
</span>