asp.net使用ashx生成图形验证码

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

 <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

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

<%@ 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>

说了半天，该是时候看看生成的验证码长什么样了