private void ComboxMaCD_Load(object sender, EventArgs e)
{
BUSGiaoVien a = new BUSGiaoVien();
DataTable dt = a.MaCDDayCombobox();
dt.Columns.Add("macd", typeof(string));
dt.Dispose();
cbxMaChuyenDeTTDK.ValueMember = "macd";
cbxMaChuyenDeTTDK.DataSource = dt;
cbxMaCDDiem.ValueMember = "macd";
cbxMaCDDiem.DataSource = dt;
}