private void cboMaSp_SelectedIndexChanged(object sender, EventArgs e) { if (cboMaSp.SelectedIndex == -1) { return; } px.MaSp = int.Parse(cboMaSp.Text); cboTenSp.DataSource = pxbll.HienThiTenSpTheoMaSp(px); cboSlcl.DataSource = pxbll.TongSoLuongTonTheoMaSp(px); cboGiaSanPham.DataSource = pxbll.SelectGiaThanhSanPham(px); double giaSp = double.Parse(cboGiaSanPham.Text); PhieuXuatHang.Money = giaSp; cboGiaSanPham.Text = giaSp.ToString("0,00.##"); }