ASP.NET(C#) 生成随机验证码

作者佚名技术来源 NET编程浏览发布时间 2012-04-12

源程序如下：

using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Collections.Generic;
using System.Text;
using System.IO;
using System.Web;

/// <summary>
///
/// ** asp.net(C#) 生成验证码 **
///
/// File: GenerateCheckCode.cs
///
/// Author:ASP.NET学习网
///
///
/// www.17aspx.com
/
/// </summary>
public class GenerateCheckCode
{
    private static string chkCode;

    public static MemoryStream GenCheckCode()
    {
        //颜色列表，用于验证码、噪线、噪点
        Color[] color ={ Color.Tomato, Color.OrangeRed, Color.Olive, Color.Gold, Color.GreenYellow,
                           Color.Blue, Color.LawnGreen, Color.Lime, Color.MediumSpringGreen, Color.Aqua, Color.RoyalBlue, Color.MediumBlue,
                           Color.BlueViolet, Color.MediumOrchid, Color.Fuchsia, Color.DeepPink, Color.HotPink };

        //字体列表，用于验证码
        string[] font = { "Times New Roman", "MS Mincho", "Book Antiqua", "Gungsuh", "PMingLiU" };

        //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();

        chkCode = string.Empty;

        //生成验证码字符串
        for (int i = 0; i < 4; i++)
        {
            chkCode += character[rnd.Next(character.Length)];
        }

        HttpContext.Current.Session["checkcode"] = chkCode;

        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);
        }

        //画边框
        Color col = color[rnd.Next(color.Length)];
        g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, 0, bmp.Width - 1, 0);
        g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, 0, 0, bmp.Height - 1);
        g.DrawLine(new Pen(color[rnd.Next(color.Length)]), bmp.Width - 1, 0, bmp.Width - 1, bmp.Height - 1);
        g.DrawLine(new Pen(color[rnd.Next(color.Length)]), 0, bmp.Height - 1, bmp.Width - 1, bmp.Height - 1);

        //清除该页输出缓存，设置该页无缓存
        HttpContext.Current.Response.Buffer = true;
        HttpContext.Current.Response.ExpiresAbsolute = System.DateTime.Now.AddMilliseconds(0);
        HttpContext.Current.Response.Expires = 0;
        HttpContext.Current.Response.CacheControl = "no-cache";
        HttpContext.Current.Response.AddHeader("Pragma", "No-Cache");
        HttpContext.Current.Response.Cache.SetCacheability(HttpCacheability.NoCache);

        //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);
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ContentType = "image/Png";
            return ms;
        }
        catch (Exception)
        {
            return null;
        }
        finally
        {
            //显式释放资源
            bmp.Dispose();
            g.Dispose();
        }
    }
}

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