Validando NFC

[DiomedesDominguez]

Buscar en el string postData y cambiar por los valores correspondientes:

 public bool IsNCFValid(string rnc, string ncf)
        {
            HttpWebRequest webrequest =
                   (HttpWebRequest)WebRequest.Create("https://dgii.gov.do/app/WebApps/ConsultasWeb/consultas/ncf.aspx");

            webrequest.Method = "POST";
            webrequest.ContentType = "application/x-www-form-urlencoded; charset=utf-8";
            webrequest.Headers.Add("Origin", "https://dgii.gov.do");
            webrequest.Referer = "https://dgii.gov.do/app/WebApps/ConsultasWeb/consultas/ncf.aspx";
            webrequest.UserAgent = "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/17.17134";
            webrequest.Headers.Add("X-MicrosoftAjax", "Delta=true");
            webrequest.Headers.Add("Cache-Control", "no-cache");
            webrequest.Accept = "*/*";
            webrequest.Headers.Add("Accept-Language", "en-US,en;q=0.8,es-US;q=0.5,es;q=0.3");
            webrequest.Headers.Add("Accept-Encoding", "gzip, deflate, br");
            webrequest.KeepAlive = true;
            webrequest.Headers.Add("Cookie", "NSC_EHJJ_efgbvmu_mcwt=ffffffffc3a0e53e45525d5f4f58455e445a4a423660; _ga=GA1.3.1057587116.1543410096; _gid=GA1.3.2007075897.1544454483; NSC_EHJJ_TTM_BQQ_MCWT=ffffffffc3a0e52245525d5f4f58455e445a4a42378b");

            webrequest.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
            string postData = $"ctl00%24smMain=ctl00%24upMainMaster%7Cctl00%24cphMain%24btnConsultar&__EVENTTARGET=&__EVENTARGUMENT=&__VIEWSTATE=%2FwEPDwUJNTM1NDc0MDQ5ZGRCFUYoDcVRgzEntcKfSuvPnC2VhA%3D%3D&__EVENTVALIDATION=%2FwEWBAKh8pDuCgK%2B9LSUBQLfnOXIDAKErv7SBhjZB34%2F%2FpbvvJzrbkFCGGPRElcd&ctl00%24cphMain%24txtRNC={rnc}&ctl00%24cphMain%24txtNCF={ncf}&__ASYNCPOST=true&ctl00%24cphMain%24btnConsultar=Consultar";

            UTF8Encoding encoding = new UTF8Encoding();
            byte[] data = encoding.GetBytes(postData.ToString());

            // Set the content length of the string being posted.
            webrequest.ContentLength = data.Length;

            System.IO.Stream newStream = webrequest.GetRequestStream();
            newStream.Write(data, 0, data.Length);
            newStream.Close();

            HttpWebResponse response = (HttpWebResponse)webrequest.GetResponse();

            using (System.IO.StreamReader reader = new System.IO.StreamReader(response.GetResponseStream(), encoding))
            {
                string responseText = reader.ReadToEnd();
                Console.WriteLine(responseText);
                return responseText.Contains(" válido");
            }
        }