ASP.NET1.1验证码产生的原理及应用

ASP.NET1.1验证码实现原理

通过随机函数产生验证码元素，将数值型的验证码元素转换成字符型然后再连成字符串，将验证码字符串写入Cookie以供验证时调用。

通过后台动态绘制位图的方法，绘制一个指定大小的位图，然后在空白位图画出底纹、验证码字体、和边框。

ASP.NET1.1验证码实现代码

(1)Login.aspx（登录页前台）

< %@ Page language="c#" Codebehind="Login.aspx.cs" AutoEventWireup="false" Inherits="Validator.Login" %>  
< !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >  
< HTML>  
    < HEAD>  
        < title>Login< /title>  
        < meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">  
        < meta name="CODE_LANGUAGE" Content="C#">  
        < meta name="vs_defaultClientScript" content="JavaScript">  
        < meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">  
    < /HEAD>  
    < body MS_POSITIONING="GridLayout">  
        < form id="Form1" method="post" runat="server">  
            < asp:button id="Button1" style="Z-INDEX: 101; LEFT: 128px; POSITION: absolute; TOP: 64px" runat="server" 
                Width="96px" Text="提交">< /asp:button>  
            < IMG src="CheckCode.aspx">  
            < asp:label id="lblMessage" style="Z-INDEX: 102; LEFT: 16px; POSITION: absolute; TOP: 128px" 
                runat="server">< /asp:label>  
            < asp:textbox id="txtCheckCode" style="Z-INDEX: 103; LEFT: 16px; POSITION: absolute; TOP: 64px" 
                runat="server" Width="88px">< /asp:textbox>  
        < /form>  
    < /body>  
< /HTML>  

(2)Login.aspx.cs(登录页后台)

using System;  
using System.Collections;  
using System.ComponentModel;  
using System.Data;  
using System.Drawing;  
using System.Web;  
using System.Web.SessionState;  
using System.Web.UI;  
using System.Web.UI.WebControls;  
using System.Web.UI.HtmlControls;  
 
namespace Validator  
{  
    /**//// < summary>  
    /// Login 的摘要说明。  
    /// < /summary>  
    public class Login : System.Web.UI.Page  
    {  
        protected System.Web.UI.WebControls.Button Button1;  
        protected System.Web.UI.WebControls.Label lblMessage;  
        protected System.Web.UI.WebControls.TextBox txtCheckCode;  
      
        private void Page_Load(object sender, System.EventArgs e)  
        {  
            // 在此处放置用户代码以初始化页面  
        }  
 
        Web 窗体设计器生成的代码#region Web 窗体设计器生成的代码  
        override protected void OnInit(EventArgs e)  
        {  
            //  
            // CODEGEN: 该调用是 asp.net Web 窗体设计器所必需的。  
            //  
            InitializeComponent();  
            base.OnInit(e);  
        }  
          
        /**//// < summary>  
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改  
        /// 此方法的内容。  
        /// < /summary>  
        private void InitializeComponent()  
        {      
            this.Button1.Click += new System.EventHandler(this.Button1_Click);  
            this.Load += new System.EventHandler(this.Page_Load);  
 
        }  
        #endregion  
 
        private void Button1_Click(object sender, System.EventArgs e)  
        {  
            if(Request.Cookies["CheckCode"] == null)   
            {  
                lblMessage.Text = "您的浏览器设置已被禁用 Cookies，您必须设置浏览器允许使用 Cookies 选项后才能使用本系统。";  
                lblMessage.Visible = true;  
                return;  
            }  
            if(String.Compare(Request.Cookies["CheckCode"].Value, txtCheckCode.Text, false) != 0) //参数为false时为区分大小写  
            {  
                lblMessage.Text = "验证码错误，请输入正确的验证码。";  
                lblMessage.Visible = true;  
                return;  
            }   
            else   
            {  
                lblMessage.Text = "通过验证";  
                lblMessage.Visible = true;  
                return;  
            }  
        }  
    }  
}  
 

(3) CheckCode.aspx(验证页前台)

< %@ Page language="c#" Codebehind="CheckCode.aspx.cs" AutoEventWireup="false" Inherits="Validator.CheckCode" %>  
< !DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >   
 
< html>  
  < head>  
    < title>CheckCode< /title>  
    < meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">  
    < meta name="CODE_LANGUAGE" Content="C#">  
    < meta name=vs_defaultClientScript content="JavaScript">  
    < meta name=vs_targetSchema content="http://schemas.microsoft.com/intellisense/ie5">  
  < /head>  
  < body MS_POSITIONING="GridLayout">  
      
    < form id="Form1" method="post" runat="server">  
        < FONT face="宋体">< /FONT>  
    < /form>  
      
  < /body>  
< /html>  
 

(4)CheckCode.aspx.cs(验证页后台)

using System;  
using System.Collections;  
using System.ComponentModel;  
using System.Data;  
using System.Drawing;  
using System.Web;  
using System.Web.SessionState;  
using System.Web.UI;  
using System.Web.UI.WebControls;  
using System.Web.UI.HtmlControls;  
 
namespace Validator  
{  
    /**//// < summary>  
    /// CheckCode 的摘要说明。  
    /// < /summary>  
    public class CheckCode : System.Web.UI.Page  
    {  
        private void Page_Load(object sender, System.EventArgs e)  
        {  
            // 在此处放置用户代码以初始化页面  
            this.CreateCheckCodeImage(GenerateCheckCode());  
        }  
 
        Web 窗体设计器生成的代码#region Web 窗体设计器生成的代码  
        override protected void OnInit(EventArgs e)  
        {  
            //  
            // CODEGEN: 该调用是 asp.net Web 窗体设计器所必需的。  
            //  
            InitializeComponent();  
            base.OnInit(e);  
        }  
          
        /**//// < summary>  
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改  
        /// 此方法的内容。  
        /// < /summary>  
        private void InitializeComponent()  
        {      
            this.Load += new System.EventHandler(this.Page_Load);  
        }  
        #endregion  
 
        private string GenerateCheckCode()  
        {                        
            int number;                        
            char code;                        
            string checkCode = String.Empty;                                     
            System.Random random = new Random();                         
            for(int i=0; i< 5; i++)                        
            {   //随机产生一个整数                               
                number = random.Next();                   
                //如果随机数是偶数 取余选择从[0-9]                               
                if(number % 2 == 0)                                      
                    code = (char)('0' + (char)(number % 10));                               
                else                               
                //如果随机数是奇数 选择从[A-Z]                                      
                    code = (char)('A' + (char)(number % 26));                                
                    checkCode += code.ToString();                        
            }                         
            Response.Cookies.Add(new HttpCookie("CheckCode", checkCode));                         
            return checkCode;                 
        }           
 
        //建立一个随机图形                 
        private void CreateCheckCodeImage(string checkCode)                 
        {                        
            if(checkCode == null || checkCode.Trim() == String.Empty)                               
                return;               
            //建立一个位图文件 确立长宽                                         
            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);                                
                //画图片的背景噪音点                               
                for(int i=0; i< 60; i++)                               
                {                                      
                    int x = random.Next(image.Width);                                      
                    int y = random.Next(image.Height);                                       
                    image.SetPixel(x, y, Color.FromArgb(random.Next()));                               
                }                   
                //把产生的随机数以字体的形式写入画面                               
                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();                        
            }                 
        }  
    }  
}  
 

ASP.NET1.1验证码主要函数分析

1、通过随机函数(Random)先产生验证码组成元素(这里为五位) 并将其转换为字符串