void NapMonHoc() { DataTable dt = new DataTable(); bus = new BUS_Diem(); dt = bus.showdata_MonHoc(); var item = new Dictionary <string, string>(); foreach (DataRow dr in dt.Rows) { item.Add(dr["MaMH"].ToString(), dr["MaMH"].ToString() + " - " + dr["TenMH"].ToString()); } cbMaMH.DataSource = new BindingSource(item, null); cbMaMH.DisplayMember = "Value"; cbMaMH.ValueMember = "Key"; }