private void cbxMaKH_SelectedIndexChanged(object sender, EventArgs e)
{
if (cbxMaKH.Text == "")
{
txtTenKH.Text = "";
txtDiaChi.Text = "";
}
txtTenKH.Text = BLL.showTenTheoMaKH(cbxMaKH.Text);
txtDiaChi.Text = BLL.showDiaChiTheoMaKH(cbxMaKH.Text);
txtDienThoai.Text = BLL.showDienThoaiTheoMaKH(cbxMaKH.Text);
LoadDataGridView();
//if (BLL.showTongTienTheoMaKH(cbxMaKH.Text, DateTime.Parse(dtpNgayXuat.Text)) == "")
//{
// txtTongTien.Text = "0";
//}
//else
// txtTongTien.Text = BLL.showTongTienTheoMaKH(cbxMaKH.Text, DateTime.Parse(dtpNgayXuat.Text));
}
