private bool KiemTraTraCuuSach()
{
var slSachSeMuon = dgvSachMuon.Rows.Count - 1;
var slSachToiDa = DocGia_BUS.LaySachMuonToiDa(txtMaDocGia.Text.ToInt32());
if (slSachToiDa == null)
{
return(false);
}
if (slSachSeMuon == slSachToiDa)
{
return(false);
}
return(true);
}