XmlDocument xmlDoc = new XmlDocument();
                xmlDoc.Load(FileName);
                string pwd = "12345";
                Encoding enc = Encoding.UTF8;
                byte[] postBytes = enc.GetBytes(xmlDoc.OuterXml);
                //label1.Text = xmlDoc.ToString();  
            
                SecureString password = new SecureString();

                for (int i = 0; i < pwd.Length; i++)
                    password.AppendChar(pwd[i]);
           
                X509Certificate2 cert = new X509Certificate2("foatov.pfx", password);

               // ServicePointManager.CertificatePolicy = new CertPolicy();
                HttpWebRequest Request = (HttpWebRequest)WebRequest.Create("https://test-crs.rs-cb.ru/A2A/request.ashx");
                Request.ProtocolVersion = HttpVersion.Version11;
               // Request.MaximumAutomaticRedirections = 4;
               // Request.MaximumResponseHeadersLength = 4;
               // Request.Proxy = new WebProxy("127.0.0.1", 8888);
                Request.Credentials = CredentialCache.DefaultCredentials;
                Request.ContentType = "text/xml";


                Request.ContentLength = postBytes.Length;//xmlDoc.OuterXml.Length; //postBytes;
                Request.ClientCertificates.Add(cert);
                Request.UserAgent = "Mozilla/5.0 (compatible; MSIE 10.0; Windows NT 6.1; WOW64; Trident/6.0)";
                Request.Method = "POST";

                Request.AllowAutoRedirect = true;
                Request.Referer = "https://test-crs.rs-cb.ru/";
                CookieContainer cookieCont = new CookieContainer();
                Request.CookieContainer = cookieCont;

                Stream dataStream = Request.GetRequestStream();
                dataStream.Write(postBytes, 0, postBytes.Length);
                dataStream.Close();

                HttpWebResponse Response = (HttpWebResponse)Request.GetResponse();


                string html = new StreamReader(Response.GetResponseStream(),
                                   Encoding.UTF8).ReadToEnd();

X509Store storeMy = new X509Store(StoreName.My,
StoreLocation.CurrentUser);
storeMy.Open(OpenFlags.ReadOnly);

X509Certificate2Collection signerCertsColl = new
X509Certificate2Collection();
X509Certificate2Collection foundCertColl = storeMy.
Certificates.Find(X509FindType.FindBySubjectName,
"Имя сертификата", false);
Request.ClientCertificates.Add(foundCertColl[0]);