C#获取登录验证码图片

// 添加MSHTML引用
// 添加MSHTML引用
// 添加MSHTML引用

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using mshtml;
using System.Threading;
using System.Runtime.InteropServices;

namespace ViewYZM
{
        //要发信息数据结构，作为SendMessage函数的LParam参数
        public struct SENDDATASTRUCT
        {
            public IntPtr dwData;       //附加一些个人自定义标志信息,自己喜欢
            public int DataLength;      //信息的长度
            [MarshalAs(UnmanagedType.LPStr)]
            public string lpData;       //要发送的信息
        }

        

    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        //自定义的消息
        public const int USER = 0x500;
        public const int MSG_VEIW_YZM = USER + 1;
        public IntPtr mMainHandle = IntPtr.Zero;

        //消息发送API
        [DllImport("User32.dll", EntryPoint = "SendMessage")]
        private static extern int SendMessage(
            IntPtr hWnd,        // 信息发住的窗口的句柄
            int Msg,            // 消息ID
            int wParam,         // 参数1
            ref SENDDATASTRUCT lParam // 参数2   [MarshalAs(UnmanagedType.LPTStr)]StringBuilder lParam
        );

       
        string mWerbUrl = "http://xxxxxx";
        string mYmzUrl = string.Empty;

        private void Form1_Load(object sender, EventArgs e)
        {
            mMainHandle = this.Handle;

            // http://xxxx/getCaptcha
            mYmzUrl = mWerbUrl + "/webwcf/BidCmd.svc/WebCmd/getCaptcha"; // 验证码图片url

            webBrowser.DocumentCompleted += new WebBrowserDocumentCompletedEventHandler(webBrowser_DocumentCompleted);
            webBrowser.Navigate(mWerbUrl);


            //this.ptYzm.Image = null;
            //this.ptYzm.WaitOnLoad = false; //设置为异步加载图片
            //this.ptYzm.SizeMode = PictureBoxSizeMode.Normal;
            //this.ptYzm.LoadAsync(mYmzUrl);

        }

        /// <summary>
        /// 网页加载完毕 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void webBrowser_DocumentCompleted(object sender, EventArgs e)
        {
            // 网页加载完成 此时验证码图片不一定已经加载
            // 为了保险，开个线程等待几秒钟，然后再获取即可
            Thread thd = new Thread(ThreadViewYzm);
            thd.Start();
        }

        private void ThreadViewYzm(object prm)
        {
            Thread.Sleep(1000 * 5); // 等待验证图片加载完成
            SENDDATASTRUCT myData = new SENDDATASTRUCT();
            SendMessage(mMainHandle, MSG_VEIW_YZM, 0, ref myData);

        }

        /// <summary>
        /// 获取验证码方法
        /// </summary>
        /// <param name="WebControlName"></param>
        /// <param name="ImgeTag"></param>
        /// <returns></returns>
        private Image GetCodeImage(WebBrowser WebControlName, HtmlElement ImgeTag)
        {
            HTMLDocument hdoc = (HTMLDocument)WebControlName.Document.DomDocument;
            HTMLBody hbody = (HTMLBody)hdoc.body;
            IHTMLControlRange hcr = (IHTMLControlRange)hbody.createControlRange();
            IHTMLControlElement hImg = (IHTMLControlElement)ImgeTag.DomElement;
            hcr.add(hImg);
            hcr.execCommand("Copy", false, null);
            Image CodeImage = Clipboard.GetImage();
            return CodeImage;
        }

        private void btnGetYzm_Click(object sender, EventArgs e)
        {
            HtmlElement ImageCodeTag = webBrowser.Document.GetElementById("imgcode");
            Image FinalImage = GetCodeImage(webBrowser, ImageCodeTag);
            this.ptYzm.Image = FinalImage;
        }

        ///重写窗体的消息处理函数DefWndProc，从中加入自己定义消息　MYMESSAGE　的检测的处理入口
        protected override void DefWndProc(ref Message m)
        {
            switch (m.Msg)
            {
                //接收自定义消息MYMESSAGE，并显示其参数
                case MSG_VEIW_YZM:
                    btnGetYzm_Click(null, null);
                    break;
                default:
                    base.DefWndProc(ref m);
                    break;
            }
        }

    }
}