自制加法验证码

写一个一般处理程序做一个加法验证码：

<%@ WebHandler Language="C#" Class="Handler" %>using System;using System.Web;using System.Web.SessionState;using System.Drawing;public class Handler : IHttpHandler, IRequiresSessionState {    public void ProcessRequest(HttpContext context) {        Random Rd = new Random();        int first = Rd.Next(10, 20);        int second = Rd.Next(0, 9);        int result = first + second;        HttpContext.Current.Session["yz"] = result;        string checkCode = first.ToString() + " + " + second.ToString() + " = ?";        int iwidth = (int)(checkCode.Length * 11.5);        System.Drawing.Bitmap image = new System.Drawing.Bitmap(70, 20);        Graphics g = Graphics.FromImage(image);        Font f = new System.Drawing.Font("Arial", 9, System.Drawing.FontStyle.Bold);        Brush b = new System.Drawing.SolidBrush(Color.White);        g.Clear(Color.Blue);        g.DrawString(checkCode, f, b, 3, 3);        Pen blackPen = new Pen(Color.Black, 0);        Random rand = new Random();        System.IO.MemoryStream ms = new System.IO.MemoryStream();        string yzimg = HttpContext.Current.Server.MapPath("~/Images/yz.jpeg");        image.Save(ms, System.Drawing.Imaging.ImageFormat.Gif);        HttpContext.Current.Response.ClearContent();        HttpContext.Current.Response.ContentType = "image/GIF";        HttpContext.Current.Response.BinaryWrite(ms.ToArray());        g.Dispose();        image.Dispose();    }    public bool IsReusable {        get {            return false;        }    }}

页面调用验证码：

 

<img id="Img1" title="看不清,请换一张" alt="看不清,请换一张" style="cursor: pointer; position:relative; top:8px;" height="24"                            width="88" src="yzm.ashx?id=1" onclick="this.src+=1" />