protected void Button1_Click1(object sender, EventArgs e)
        {
            string xxx = tk.MaHoaMD5(txtMatKhau.Text);

            if (tk.KtraDangNhap(txtTaiKhoan.Text, xxx) == true)
            {
                Response.Redirect("View.aspx");
            }
            else if (tk.KtraDangNhapCus(txtTaiKhoan.Text, xxx) == true)
            {
                Response.Redirect("/Customer/ViewCustomerSignIn.aspx");
            }
            else

            {
                Response.Redirect("FormLogin.aspx");
                txtTaiKhoan.Text = "";
                txtMatKhau.Text  = "";
                txtTaiKhoan.Focus();
            }
        }