c# foreach does not work

Hello,

please help me, I'm desperate and cannot find the solution.

Below is the code that does not work:

 List<sq> aList = new List<sq> ();
 compileList(sqA, ref aList);
 
 public void compileList(sq e, ref List<sq> iList){
     foreach(sq s in e.neighbors){
         compileList(s, ref iList);
     }
 }

sq class contains

 public class sq : MonoBehaviour {
     public List<sq> neighbors = new List<sq> ();
     ...
 }

but the foreach loop is not even called to every recursive neighbor : (
Neighbors are constructed like this:
sqA - sqB - sqC - sqD - sqE
where, for example sqB has neighbors sqA and sqC,
and sqA has a single neighbor sqB.

Any help much appreciated.