public int[] Indexes {get;}

MDPart oPart = m_MDPartsDatabase.Parts[0];//a valid part object
MDPropertyValue oProperty = oPart.Properties[Eplan.EplApi.MasterData.Properties.MDPartsDatabaseItem.ARTICLE_FREE_DATA_VALUE;];
if (oProperty.Definition.IsIndexed)
{
	foreach (int index in oProperty.Indexes)
	{
		MDPropertyValue oPropertyElement = oProperty[index];
		string sProperty = oPropertyElement.ToString();
	}
}