webBrowser.Document.Cookie取不到HttpOnly的Cookie，取Cookie不完整

在做数据采集时，有些网站需要输入验证码，但各网站验证码都不同，不可能有完美的识别验证码的代码，所以我也没去研究，我所采取的方案是：在winform里通过WebBrowser调用网页先手动登录系统，然后再通过webBrowser1.Document.Cookie获取其Cookie，再将其用到HttpWebRequest里用来访问自己需要的页。
一直用的都没有问题，但最近在对一个网站操作时总是不能获取完整Cookie，百思不得其解，使用Fiddler2对比发现，不能获取到的Cookie里最后有一个HttpOnly的标识，顺藤摸瓜发现原来webBrowser1.Document.Cookie里是取不到HttpOnly的Cookie的，也找到解决方法：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.ComponentModel;
using System.Net;
using System.Runtime.InteropServices;
using System.Security;
using System.Security.Permissions;

namespace ToutiaoTool
{
internal sealed class NativeMethods
{
#region enums

    public enum ErrorFlags
    {
        ERROR_INSUFFICIENT_BUFFER = 122,
        ERROR_INVALID_PARAMETER = 87,
        ERROR_NO_MORE_ITEMS = 259
    }

    public enum InternetFlags
    {
        INTERNET_COOKIE_HTTPONLY = 8192, //Requires IE 8 or higher   
        INTERNET_COOKIE_THIRD_PARTY = 131072,
        INTERNET_FLAG_RESTRICTED_ZONE = 16
    }

    #endregion

    #region DLL Imports

    [SuppressUnmanagedCodeSecurity, SecurityCritical, DllImport("wininet.dll", EntryPoint = "InternetGetCookieExW", CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
    internal static extern bool InternetGetCookieEx([In] string Url, [In] string cookieName, [Out] StringBuilder cookieData, [In, Out] ref uint pchCookieData, uint flags, IntPtr reserved);

    #endregion
}


/// <SUMMARY></SUMMARY>   
/// 取得WebBrowser的完整Cookie。   
/// 因为默认的webBrowser1.Document.Cookie取不到HttpOnly的Cookie   
///    
public class FullWebBrowserCookie
{

    [SecurityCritical]
    public static string GetCookieInternal(Uri uri, bool throwIfNoCookie)
    {
        uint pchCookieData = 0;
        string url = UriToString(uri);
        uint flag = (uint)NativeMethods.InternetFlags.INTERNET_COOKIE_HTTPONLY;

        //Gets the size of the string builder   
        if (NativeMethods.InternetGetCookieEx(url, null, null, ref pchCookieData, flag, IntPtr.Zero))
        {
            pchCookieData++;
            StringBuilder cookieData = new StringBuilder((int)pchCookieData);

            //Read the cookie   
            if (NativeMethods.InternetGetCookieEx(url, null, cookieData, ref pchCookieData, flag, IntPtr.Zero))
            {
                DemandWebPermission(uri);
                return cookieData.ToString();
            }
        }

        int lastErrorCode = Marshal.GetLastWin32Error();

        if (throwIfNoCookie || (lastErrorCode != (int)NativeMethods.ErrorFlags.ERROR_NO_MORE_ITEMS))
        {
            throw new Win32Exception(lastErrorCode);
        }

        return null;
    }

    private static void DemandWebPermission(Uri uri)
    {
        string uriString = UriToString(uri);

        if (uri.IsFile)
        {
            string localPath = uri.LocalPath;
            new FileIOPermission(FileIOPermissionAccess.Read, localPath).Demand();
        }
        else
        {
            new WebPermission(NetworkAccess.Connect, uriString).Demand();
        }
    }

    private static string UriToString(Uri uri)
    {
        if (uri == null)
        {
            throw new ArgumentNullException("uri");
        }

        UriComponents components = (uri.IsAbsoluteUri ? UriComponents.AbsoluteUri : UriComponents.SerializationInfoString);
        return new StringBuilder(uri.GetComponents(components, UriFormat.SafeUnescaped), 2083).ToString();
    }
}

}

refer： http://blog.csdn.net/smeller/article/details/7022370