private void ComboxDead_Load(object sender, EventArgs e) { BUSGiaoVien a = new BUSGiaoVien(); DataTable dt = a.DeadCombobox(cbLopCapNhatDead.Text, IDNguoiDung); dt.Columns.Add("madead", typeof(string)); dt.Dispose(); cbMaDead.ValueMember = "madead"; cbMaDead.DataSource = dt; }