public void LoadTenNhiemVu()
{
DataTable tbNhiemVu = doan.GetTenNhiemVu();
cbbNhiemVu.DataSource = tbNhiemVu;
cbbNhiemVu.DisplayMember = "TenNhiemVu";
cbbNhiemVu.ValueMember = "TenNhiemVu";
}