获取webbrowser的cookies

[DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern bool InternetGetCookieEx(string pchURL, string pchCookieName, StringBuilder pchCookieData, ref System.UInt32 pcchCookieData, int dwFlags, IntPtr lpReserved);
        private static string GetCookies(string url)
        {
            uint datasize = 1024;
            StringBuilder cookieData = new StringBuilder((int)datasize);
            if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x2000, IntPtr.Zero))
            {
                if (datasize < 0)
                    return null;

                cookieData = new StringBuilder((int)datasize);
                if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x00002000, IntPtr.Zero))
                    return null;
            }
            return cookieData.ToString();
        }