ASP.NET 2.0 HttpHandler实现生成图片验证码

 1. 处理程序文件 ValidateImageHandler.ashx代码如下

<% @ WebHandler Language = " C# "  Class = " ValidateImageHandler "   %>

using  System;
using  System.Web;
using  System.Web.SessionState;
using  System.Drawing;
using  System.Drawing.Imaging;
using  System.Text;

/**/ /// <summary>
/// ValidateImageHandler 生成网站验证码功能
/// </summary>
public   class  ValidateImageHandler : IHttpHandler, IRequiresSessionState
{
    int intLength = 5;               //长度
    string strIdentify = "Identify"; //随机字串存储键值，以便存储到Session中
    public ValidateImageHandler()
    {        
    }

    /**//// <summary>
    ///  生成验证图片核心代码
    /// </summary>
    /// <param name="hc"></param>
    public void ProcessRequest(HttpContext hc)
    {
        //设置输出流图片格式
        hc.Response.ContentType = "image/gif";
        
        Bitmap b = new Bitmap(200, 60);
        Graphics g = Graphics.FromImage(b);
        g.FillRectangle(new SolidBrush(Color.YellowGreen), 0, 0, 200, 60);
        Font font = new Font(FontFamily.GenericSerif, 48, FontStyle.Bold, GraphicsUnit.Pixel);
        Random r = new Random();

        //合法随机显示字符列表
        string strLetters = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
        StringBuilder s = new StringBuilder();
        
        //将随机生成的字符串绘制到图片上
        for (int i = 0; i < intLength; i++)
        {
            s.Append(strLetters.Substring(r.Next(0, strLetters.Length - 1), 1));
            g.DrawString(s[s.Length - 1].ToString(), font, new SolidBrush(Color.Blue), i * 38, r.Next(0, 15));
        }

        //生成干扰线条
        Pen pen = new Pen(new SolidBrush(Color.Blue), 2);
        for (int i = 0; i < 10; i++)
        {
            g.DrawLine(pen, new Point(r.Next(0, 199), r.Next(0, 59)), new Point(r.Next(0, 199), r.Next(0, 59)));
        }
        b.Save(hc.Response.OutputStream, ImageFormat.Gif);
        hc.Session[strIdentify] = s.ToString(); //先保存在Session中，验证与用户输入是否一致
        hc.Response.End();
   
    }
    
    /**//// <summary>
    /// 表示此类实例是否可以被多个请求共用(重用可以提高性能)
    /// </summary>
    public bool IsReusable
    {
        get
        {
            return true;
        }
    }
}

2.前台代码

 

<% @ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default"  %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >
< html  xmlns ="http://www.w3.org/1999/xhtml" >
< head  runat ="server" >
     < title > ImageValidateCode_HttpHandler </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
         < div >
             &nbsp; < br  />
             < br  />
             < asp:Login  ID ="Login1"  runat ="server"  BackColor ="#EFF3FB"  BorderColor ="#B5C7DE"  BorderPadding ="4"
                BorderStyle ="Solid"  BorderWidth ="1px"  Font-Names ="Verdana"  Font-Size ="0.8em"
                ForeColor ="#333333"  OnAuthenticate ="Login1_Authenticate" >
                 < TitleTextStyle  BackColor ="#507CD1"  Font-Bold ="True"  Font-Size ="0.9em"  ForeColor ="White"   />
                 < InstructionTextStyle  Font-Italic ="True"  ForeColor ="Black"   />
                 < TextBoxStyle  Font-Size ="0.8em"   />
                 < LoginButtonStyle  BackColor ="White"  BorderColor ="#507CD1"  BorderStyle ="Solid"  BorderWidth ="1px"
                    Font-Names ="Verdana"  Font-Size ="0.8em"  ForeColor ="#284E98"   />
                 < LayoutTemplate >
                     < table  border ="0"  cellpadding ="4"  cellspacing ="0"  style ="border-collapse: collapse" >
                         < tr >
                             < td  style ="width: 292px" >
                                 < table  border ="0"  cellpadding ="0" >
                                     < tr >
                                         < td  align ="center"  colspan ="2"  style ="font-weight: bold; font-size: 0.9em; color: white;
                                            background-color: #507cd1" >
                                            登录 </ td >
                                     </ tr >
                                     < tr >
                                         < td  align ="left"  style ="width: 84px; height: 31px;" >
                                             < asp:Label  ID ="UserNameLabel"  runat ="server"  AssociatedControlID ="UserName" > 用户名: </ asp:Label ></ td >
                                         < td  style ="height: 31px; width: 215px;" >
                                             < asp:TextBox  ID ="UserName"  runat ="server"  Font-Size ="0.8em"  Width ="113px" ></ asp:TextBox >
                                             < asp:RequiredFieldValidator  ID ="UserNameRequired"  runat ="server"  ControlToValidate ="UserName"
                                                ErrorMessage ="必须填写“用户名”。"  ToolTip ="必须填写“用户名”。"  ValidationGroup ="Login1" > * </ asp:RequiredFieldValidator >
                                         </ td >
                                     </ tr >
                                     < tr >
                                         < td  align ="left"  style ="width: 84px" >
                                             < asp:Label  ID ="PasswordLabel"  runat ="server"  AssociatedControlID ="Password" > 密码: </ asp:Label ></ td >
                                         < td  style ="width: 215px" >
                                             < asp:TextBox  ID ="Password"  runat ="server"  Font-Size ="0.8em"  TextMode ="Password" ></ asp:TextBox >
                                             < asp:RequiredFieldValidator  ID ="PasswordRequired"  runat ="server"  ControlToValidate ="Password"
                                                ErrorMessage ="必须填写“密码”。"  ToolTip ="必须填写“密码”。"  ValidationGroup ="Login1" > * </ asp:RequiredFieldValidator >
                                         </ td >
                                     </ tr >
                                     < tr >
                                         < td  style ="width: 84px; height: 4px;"  align ="left" >
                                            验证码: </ td >
                                         < td  valign ="middle"  style ="height: 31px; width: 215px;"  align ="left" >
                                             < asp:TextBox  ID ="TextBox1"  runat ="server"  Font-Size ="0.8em"  TextMode ="Password" ></ asp:TextBox > &nbsp;
                                             < img  width ="100px"  height ="25px"  src ="ValidateImageHandler.ashx"   /></ td >
                                     </ tr >
                                     < tr >
                                         < td  align ="left"  colspan ="2"  style ="color: red" >
                                             < asp:CheckBox  ID ="RememberMe"  runat ="server"  Text ="下次记住我。"   /> &nbsp; </ td >
                                     </ tr >
                                     < tr >
                                         < td  align ="right"  colspan ="2" >
                                             < asp:Button  ID ="LoginButton"  runat ="server"  BackColor ="White"  BorderColor ="#507CD1"
                                                BorderStyle ="Solid"  BorderWidth ="1px"  CommandName ="Login"  Font-Names ="Verdana"
                                                Font-Size ="0.8em"  ForeColor ="#284E98"  Text ="登录"  ValidationGroup ="Login1"   />
                                         </ td >
                                     </ tr >
                                 </ table >
                             </ td >
                         </ tr >
                     </ table >
                 </ LayoutTemplate >
             </ asp:Login >
         </ div >
     </ form >
</ body >
</ html >