asp.net实现验证码

这个之前（很久之前了吧）使用webform的时候使用的验证码，实现的方式也很简单。

using System;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;
using System.Text;
using System.Collections;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
namespace WebUI.yzm
{
    public partial class yzm : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            string yzmCode = 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,0-9,大写字母A-Z */
            char[] character = { '0', '1', '2', '3', '4', '5', '6', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'J',
                          'K',  'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z' };
            Random rnd = new Random();
            /* 生成验证码字符串 */
            for (int i = 0; i < 4; i++)
            {
                yzmCode += character[rnd.Next(character.Length)];
            }
            /* 存入session以便判断 */
            Session["yzm"] = yzmCode;
            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 < yzmCode.Length; i++)
            {
                string fnt = font[rnd.Next(font.Length)];
                Font ft = new Font(fnt, 18);
                Color clr = color[rnd.Next(color.Length)];
                g.DrawString(yzmCode[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.ToArray());
            }
            finally
            {
                /* 显式释放资源 */
                bmp.Dispose();
                g.Dispose();
            }
        }
    }
}
  

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