//Load Combobox
private void ComboxLop_Load(object sender, EventArgs e)
{
BUSGiaoVien orders = new BUSGiaoVien();
DataTable dt = orders.LopCombobox(IDChuyenDe, IDNguoiDung);
dt.Columns.Add("malop", typeof(string));
dt.Dispose();
cbLopCapNhatDead.ValueMember = "malop";
cbChonLopThemDead.ValueMember = "malop";
cbLopCapNhatDead.DataSource = dt;
cbChonLopThemDead.DataSource = dt;
}