asp.net使用ashx生成图形验证码的方法示例

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
{
  /// 

  /// $codebehindclassname$ 的摘要说明
  /// 
  [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 

请输入验证码: