private void Menumon()
{
DataTable dtc = new DataTable();
dtc = bd.Laydanhsachmon("A");
cbo_lau.DataSource = dtc;
cbo_lau.ValueMember = "MaMon";
cbo_lau.DisplayMember = "TenMon";
DataTable dt1 = new DataTable();
dt1 = bd.Laydanhsachmon("B");
cbo_1.DataSource = dt1;
cbo_1.ValueMember = "MaMon";
cbo_1.DisplayMember = "TenMon";
DataTable dt2 = new DataTable();
dt2 = bd.Laydanhsachmon("C");
cbo_2.DataSource = dt2;
cbo_2.ValueMember = "MaMon";
cbo_2.DisplayMember = "TenMon";
DataTable dt3 = new DataTable();
dt3 = bd.Laydanhsachmon("D");
cbo_3.DataSource = dt3;
cbo_3.ValueMember = "MaMon";
cbo_3.DisplayMember = "TenMon";
}