asp.net使用ashx生成图形验证码的方法示例_ASP.NET教程

本文实例讲述了asp.net使用ashx生成图形验证码的方法。分享给大家供大家参考，具体如下：

验证码的好处不用我多说，你们都懂的。我在网上看到有人把验证码直接写在aspx页面里，也就是说这种方式请求验证码等于请求一个页面，这样做很不科学。如下所示

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									<form id="form1" runat="server">

									  <div>

									    <asp:Image ID="Image1" runat="server" ImageUrl="Default.aspx" />

									    <br />

									    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

									    <asp:Button ID="Button1" runat="server" onclick="Button1_Click" Text="Button" />

									  </div>

									</form>

这个代码看着就觉得写代码的人比较欠揍，代码写成这样子着实郁闷。验证吗也不写点script做下切换。

下面我介绍一种方式来实现这样的功能

1. 写个ashx生成图形验证码

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									using System;

									using System.Collections;

									using System.Data;

									using System.Linq;

									using System.Web;

									using System.Web.Services;

									using System.Web.Services.Protocols;

									using System.Xml.Linq;

									using System.Web.SessionState;

									using System.Drawing;

									namespace usechecknum.ashx

									{

									  /// <summary>

									  /// $codebehindclassname$ 的摘要说明

									  /// </summary>

									  [WebService(Namespace = "http://tempuri.org/")]

									  [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]

									  public class doCreateNum : IHttpHandler,IRequiresSessionState

									  {

									    public void ProcessRequest(HttpContext context)

									    {

									      context.Response.ContentType = "text/html";

									      string checkCode = GetValidation(5); // 产生5位随机验证码字符

									      context.Session["Code"] = checkCode; //将字符串保存到Session中，以便需要时进行验证

									      System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 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);

									        // 画图片的背景噪音线

									        int i;

									        for (i = 0; i < 25; i++)

									        {

									          int x1 = random.Next(image.Width);

									          int x2 = random.Next(image.Width);

									          int y1 = random.Next(image.Height);

									          int y2 = random.Next(image.Height);

									          g.DrawLine(new Pen(Color.Silver), x1, y1, x2, y2);

									        }

									        Font font = new System.Drawing.Font("Arial", 12, (System.Drawing.FontStyle.Bold));

									        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);

									        //画图片的前景噪音点

									        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);

									        context.Response.ClearContent();

									        context.Response.ContentType = "image/Gif";

									        context.Response.BinaryWrite(ms.ToArray());

									      }

									      finally

									      {

									        g.Dispose();

									        image.Dispose();

									      }

									    }

									    public string GetValidation(int num)

									    {

									      string str = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //"或者写汉字也行"

									      string validatecode = "";

									      Random rd = new Random();

									      for (int i = 0; i < num; i++)

									      {

									        validatecode += str.Substring(rd.Next(0, str.Length), 1);

									      }

									      return validatecode;

									    }

									    public bool IsReusable

									    {

									      get

									      {

									        return false;

									      }

									    }

									  }

									}

2. 在页面上显示验证码，因为我们生成的是图形，所以可以直接写在<img/>标签里，我们只要写段简单的脚本就可以点击鼠标切换验证码了

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									<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="index.aspx.cs" Inherits="usechecknum._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>验证码的使用</title>

									</head>

									<script language="javascript" type="text/javascript">

									  function changeCode() {

									    var imgNode = document.getElementById("vimg");

									    imgNode.src = "ashx/doCreateNum.ashx?t=" + (new Date()).valueOf(); // 这里加个时间的参数是为了防止浏览器缓存的问题

									  }

									  </script>

									<body>

									  <form id="form1" runat="server">

									   请输入验证码:<input type="text" name="checknum"/><img src="ashx/doCreateNum.ashx" id="vimg" onclick="changeCode()" />

									  </form>

									</body>

									</html>