How to get parent Item type recursively

I've tried this and it doesn't repeat since you put the fix id to the related_id's Item. It always do one level I think.

Hi TU_YINING AngelaIp Could you please help me how to find this? Advance Thanks...
Recursive parent...

Here is a sample for recursive search for forward and backward.

////////////////////////////////////////////////////////////////////
///   - IN:
///     - RequestState
///     - [String] initIDs: initial IDs (csv)
///     - Properties
///     - [String] direction: forward/backward
///     - [String] itemtype: itemtype's name of RELATIONSHIP
///     - [String] is_all_level: return all levels or only the top/end
///       - 0(default): top/end only
///       - 1: all levels (all children or all parents)
///   - OUT:
///   - RequestState
///     - [String] returnIDs: target IDs (csv)
///   - newResult()
///     - 0   : normal
///     - E003: Bad Args
///     - E004: No target Items
///
////////////////////////////////////////////////////////////////////

Innovator inn = this.getInnovator();
List<string> targetList;
string direction, itemtype;

try
{
  string temp = (string)RequestState["initIDs"];
  targetList = temp.Split(',').ToList();
  RequestState.Remove("initIDs");
}
catch (Exception e)
{
  return inn.newResult("E004");
}

try
{
  direction = this.getProperty("direction");
  itemtype = this.getProperty("itemtype");
  if (direction != "forward" && direction != "backward")
  {
    throw new Exception("Unvalid parameter.");
  }
}
catch (Exception e)
{
  return inn.newResult("E003");
}

var relatedList = new List<string>();

var libraryList = new List<string>();

try
{
  while (targetList.Count != 0)
  {
    for (int i = targetList.Count - 1; i >= 0; i--)
    {
      if (libraryList.Contains(targetList[i]) == false)
      {
        Item sourceItem = inn.newItem(itemtype, "get");
        sourceItem.setAttribute("select", direction == "forward" ? "related_id" : "source_id");
        sourceItem.setProperty(direction == "forward" ? "source_id" : "related_id", targetList[i]);
        Item rtItem = sourceItem.apply();
        int rtCount = rtItem.getItemCount();
        if (rtCount == 0)
        {
          relatedList.Add(targetList[i]);
        }
        else
        {
          for (int j = 0; j < rtCount; j++)
          {
            Item resultItem = rtItem.getItemByIndex(j);
            targetList.Add(resultItem.getProperty(direction == "forward" ? "related_id" : "source_id"));
          }
        }
        libraryList.Add(targetList[i]);
      }
      targetList.RemoveAt(i);
    }
  }
}
catch (Exception e)
{
  // unknown Relationship itemtype
  return inn.newResult("E003");
}

if (this.getProperty("is_all_level") == "1")
{
  RequestState.Add("returnIDs", String.Join(",", libraryList));
}
else
{
  RequestState.Add("returnIDs", String.Join(",", relatedList));
}
return inn.newResult("0");