webBroser获取cookie

//取当前webBrowser登录后的Cookie值   
        [DllImport("wininet.dll", CharSet = CharSet.Auto, SetLastError = true)]
        static extern bool InternetGetCookieEx(string pchURL, string pchCookieName, StringBuilder pchCookieData, ref int pcchCookieData, int dwFlags, object lpReserved);
        //取出Cookie，当登录后才能取    
        private static string GetCookieString(string url)
        {
            // Determine the size of the cookie      
            int datasize = 256;
            StringBuilder cookieData = new StringBuilder(datasize);
            if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x00002000, null))
            {
                if (datasize < 0)
                    return null;
                // Allocate stringbuilder large enough to hold the cookie    
                cookieData = new StringBuilder(datasize);
                if (!InternetGetCookieEx(url, null, cookieData, ref datasize, 0x00002000, null))
                    return null;
            }
            return cookieData.ToString();
        }