public string GetObjectIDPropertyName()

QueuedTask.Run(() =>
{
  //Create a connection properties
  var kg_props =
      new KnowledgeGraphConnectionProperties(new Uri(url));
  using (var kg = new KnowledgeGraph(kg_props))
  {
    //Get the KnowledgeGraph Data Model
    using (var kg_dm = kg.GetDataModel())
    {
      var dict_types = kg_dm.GetEntityTypes();

      foreach (var kvp in dict_types)
      {
        var entity_type = kvp.Value;
        var role = entity_type.GetRole();
        //note "name" will be the same name as the corresponding
        //feature class or table in the KG's relational gdb model
        var name = entity_type.GetName();
        var alias = entity_type.GetAliasName();
        var objectIDPropertyName = entity_type.GetObjectIDPropertyName();
        //etc

      }

    }
  }
});