public bool CanExtend {get;}

{
  // Various editing operations on a network diagram
  static void EditDiagram(NetworkDiagram diagram, List<Guid> globalIDs)
  {
    // These routines generate their own editing transaction, and therefore cannot be wrapped
    // in a separate transaction. Because the editing performed by these routines cannot
    // be undone, thise routines can also not be called within an editing session. All
    // edits in the current edit session must be saved or discarded before calling these
    // routines.

    // Refresh the diagram - synchronizes it based on the latest network topology
    diagram.Update();

    // Append features to the diagram
    diagram.Append(globalIDs);

    // Overwrite the diagram with a set of features
    diagram.Overwrite(globalIDs);

    NetworkDiagramInfo info = diagram.GetDiagramInfo();
    if (info.CanExtend)
    {
      diagram.Extend(NetworkDiagramExtendType.ExtendByContainment);

      // or extend for only a set of utility network globalIDs
      diagram.Extend(NetworkDiagramExtendType.ExtendByContainment, globalIDs);
    }
    // Delete a diagram
    diagram.Delete();
  }
}