public void HienThi(DataGridView dg, BindingNavigator bn, TextBox ma, TextBox ten, ComboBox nam)
        {
            BindingSource bs = new BindingSource();

            bs.DataSource    = Data.LayDSHocKi();
            bn.BindingSource = bs;
            dg.DataSource    = bs;
            if (ma.DataBindings.Count > 0)
            {
                ma.DataBindings.RemoveAt(0);
                ten.DataBindings.RemoveAt(0);
                nam.DataBindings.RemoveAt(0);
            }

            NamHocCtrl ctrlnam = new NamHocCtrl();

            dg.Columns.Add(ctrlnam.ColumnNamHoc());
            dg.Columns.RemoveAt(2);


            ma.DataBindings.Add("Text", bs, "MAHOCKI");
            ten.DataBindings.Add("Text", bs, "TENHOCKI");

            NamHocData dataNam = new NamHocData();

            nam.DataSource    = dataNam.LayDSNamHoc();
            nam.DisplayMember = "TENNAMHOC";
            nam.ValueMember   = "MANAMHOC";

            nam.DataBindings.Add("SelectedValue", bs, "MANAM");
        }