const string LDAP_PATH = "EX://ldap.pjwstk.edu.pl";
            const string LDAP_DOMAIN = "ldap.pjwstk.edu.pl";

            using (var context = new PrincipalContext(ContextType.Domain, LDAP_DOMAIN, "pgago", "xxx"))
            {
                if (context.ValidateCredentials("pgago", "xxx"))
                {
                    using (var de = new DirectoryEntry(LDAP_PATH))
                    using (var ds = new DirectorySearcher(de))
                    {
                        var identities = new List<ClaimsIdentity> { new ClaimsIdentity("custom auth type") };

                    }
                }
            }