验证码程序

常用的生成验证码程序 ，图片效果如下：

     

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: 周振兴 (Zxjay 飘遥)
///
/// E-Mail: [email protected]
///
/// Date: 07-04-10
///
/// http://xianfen.net
///
/// </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();
        }
    }
}

使用方法如下：

新建名为 GenerateCheckCode.aspx 的文件，文件的内容为：

<%@ Page Language="C#" %>
<% Response.BinaryWrite(GenerateCheckCode.GenCheckCode().ToArray());%>

在需要验证码的地方放置的代码为：

  
    

   
     <
   
     a 
   
     href
   
     ="javascript:void(0);"
   
      onfocus
   
     ="javascript:blur();"
   
      
onclick
   
     ="document.getElementById('img1').src='Control/CheckCode.aspx?id='+ 
(new Date().getTime().toString(36));"
   
     ><
   
     img 
   
     id
   
     ="img1"
   
      
style
   
     ="float: left; margin-top: 1px; margin-left: 3px;"
   
      class
   
     ="imgcode"
   
      
title
   
     ="看不清，换一张！"
   
      src
   
     ="Control/CheckCode.aspx"
   
      
   
     />
</
   
     a
   
     >
  
    

以上js代码为的是实现验证码的刷新。
验证码输入框中的字符和 Session["checkcode"] 的值比较是否相同来确定验证是否通过。