C# webBrowser登录提示验证码错误

Question

今天偶然发现我们学校的出校访问网页是数字验证码，于是想拿来破解。思路就是普通的抓取元素，然后填入表单，然后发现一切顺利，账号密码和验证码都填进去了。然后登陆发现
永远提示验证码错误，郁闷啊，手动输入也是验证码错误，但是在浏览器内是可以使用的，不知道问题在哪里

Answer 1

代码如下

 using System;
using System.Windows.Forms;

namespace 登陆网页
{

    public partial class Form1 : Form
    {

        public Form1()
        {
            InitializeComponent();
            webBrowser1.Navigate("http://wall.usts.edu.cn/jf6/zizhufuwu.php");
        }
        private void button1_Click(object sender, EventArgs e)
        {
            webBrowser1.Refresh();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //while (true)
            //{

                HtmlDocument doc = webBrowser1.Document;
                HtmlElement yanzhengma = doc.GetElementById("jy");
            string code = yanzhengma.All[0].All[0].All[12].InnerHtml;
            code = code[0].ToString() + code[1] + code[2] + code[3];
            string html = yanzhengma.All[0].All[0].All[10].InnerHtml;
            string result="";
            for (int i = 0; i < html.Length; i++)
            {
                if (html[i] != '>')
                    continue;
                i+=2;
                result = html[i].ToString() + html[i+1] + html[i+2] + html[i+3];
                //MessageBox.Show(result);
            }
            int password=111111;
            doc.GetElementById("UserName").SetAttribute("value", "1234");
            doc.GetElementById("uPassWord").SetAttribute("value", password.ToString());
            doc.GetElementById("yianzhengma").SetAttribute("value", result);
            //yanzhengma.All[0].All[0].All[11].SetAttribute("value", code);

            doc.GetElementById("B1").InvokeMember("click");
            //if (name != null)
            //    name.SetAttribute("value", a.ToString());
            //a++;
            //HtmlElement pass = doc.GetElementById("p");
            //if (pass != null)
            //    pass.SetAttribute("value", "123");
            //HtmlElement login = webBrowser1.Document.GetElementById("login_button");
            //if (login != null)
            //    login.InvokeMember("click");
            //    Application.DoEvents();
            //}
        }
    }
}