EF6 PostgreSQL SSL

                NpgsqlConnection conSql2 = new NpgsqlConnection();
                conSql2.ConnectionString = "<PGserver>;User Id=<UserName>;Password=<***>;Port=5432;Database=<DB>;SSL Mode=Require";
                conSql2.ProvideClientCertificatesCallback += ProvideClientCertificatesCallback;
                conSql2.Open();
}

        static void ProvideClientCertificatesCallback(X509CertificateCollection clientCerts)
        {
            clientCerts.Add(new X509Certificate2(<UserName.pfx>, ""));
        }

            using (AppIdentityDbContext appIdentDB = new AppIdentityDbContext())
            {
                if (appIdentDB.Database.Exists()) blnIsExists = true;

    public class AppIdentityDbContext : IdentityDbContext<AppUser>
    {
        public AppIdentityDbContext() : base("name=DBcontext") {}
 
 
        static AppIdentityDbContext()
        {
            Database.SetInitializer<AppIdentityDbContext>(new IdentityDbInit());
        }
 
        public static AppIdentityDbContext Create()
        {
            return new AppIdentityDbContext();
        }
 
        protected override void OnModelCreating(DbModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
        }
 
    }   // public class AppIdentityDbContext : IdentityDbContext<AppUser>

protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    => optionsBuilder .UseNpgsql("...",  o => o.ProvideClientCertificatesCallback()...);