protected void btnThem_Click(object sender, EventArgs e)
 {
     try
     {
         string ten = txtTen.Text;
         string dt = txtDienThoai.Text;
         string email = txtEmail.Text;
         string ngaysinh = txtNgay.Text;
         string diachi = txtDiaChi.Text;
         int chucvu = int.Parse(drChucVu.SelectedValue.ToString());
         string maten = txtMaTenN.Text;
         float rate = float.Parse(txtRate.Text);
         string user = txtuser.Text;
         string pass = GetMD5Hash(txtpass.Text);
         string fullname = txtFullName.Text;
         GiamDinhVienDAO gdvdao = new GiamDinhVienDAO();
         gdvdao.ThemGiamDinhVien(ten, dt, email, ngaysinh, diachi, chucvu, user, pass, maten, rate, fullname);
         HienThiDanhSach();
         danhsach.Visible = true;
         them.Visible = false;
     }
     catch (Exception ex)
     {
         Response.Write("<script> alert('Không để trống thông tin!');</script>");
     }
 }