CutList feature CustomPropertyManager has no properties

I'm trying to access the custom properties of a sheetmetal cutlist feature like this:

"Zuschnittslistenelement1" is the german name for "Cut-List-Item1"

IModelDoc2 partModel = _solidWorks.OpenDoc6(fileName, (int)swDocumentTypes_e.swDocPART,

  (int)swOpenDocOptions_e.swOpenDocOptions_LoadModel,

  string.Empty, ref loadError, ref loadWarnings);

_solidWorks.ActivateDoc2(fileName, false, loadError);

object featuresObject = partModel.FeatureManager.GetFeatures(true);

object[] features = featuresObject as object[];

Feature cutList = null;

foreach (object featureObject in features)

{

  Feature feature1 = featureObject as Feature;

  if (feature1.Name == "Zuschnittslistenelement1")

  {

  cutList = feature1;

  }

}

if (cutList != null)

{

  CustomPropertyManager propertyManager = cutList.CustomPropertyManager;

  string resolvedRahmenLaenge;

  string rahmenLaenge;

  propertyManager.Get4("Rahmenlänge", false, out rahmenLaenge, out resolvedRahmenLaenge);

  string resolvedRahmenBreite;

  string rahmenBreite;

  propertyManager.Get4("Rahmenbreite", false, out rahmenBreite, out resolvedRahmenBreite);

}

propertyManager.Count is 0.

SolidworksApi macros