Setting Duct Width and Height Requires Regeneration

Whenever you have a problem modifying or querying the model with your Revit plug-in, one of the first things to check is always your regeneration mode. If you are using the manual regeneration option, you need to check whether you possibly omitted a required intermediate regeneration call. It seems that there can never be enough reminders of this. Here is another case at hand:

Question: I am sizing rectangular duct fittings through the API, and I noticed that the different dimensions for width and height must be set in different transactions. Otherwise, you lose the first size change when the second one is made.

Is this a feature or a bug?

The requirement to start and commit a separate transaction for each dimension change makes sizing of the network quite clumsy and even slow with larger drawings.

Here are two simple example code snippets in managed C++ setting the width and height of an elbow to 500x500 mm. They have both the TransactionMode and the RegenerationOption set to Manual. The first one uses a single transaction and does not work. The second uses two transactions and does.

Here is the first test with the size changes in same transaction:

Result AddinTest1::Execute(
  ExternalCommandData^ commandData, 
  System::String^% message, 
  ElementSet^ elements)
{  
  Document ^doc = commandData->Application
    ->ActiveUIDocument->Document;
 
  // Duct/bend IDs in example project
  
  int west_east   = 505594;
  int north_south = 505598;
  int bend_id     = 505610;
 
  ElementId ^elemId = gcnew ElementId(west_east);
  Element ^ductElem1 = doc->Element::get(elemId);
 
  elemId = gcnew ElementId(north_south);
  Element ^ductElem2 = doc->Element::get(elemId);
 
  elemId = gcnew ElementId(bend_id);
  Element ^bendElem1 = doc->Element::get(elemId);
 
  FamilyInstance ^bend 
    = safe_cast<FamilyInstance^>(bendElem1);
 
  ConnectorSet ^cSet 
    = bend->MEPModel->ConnectorManager->Connectors;
 
  Transaction tr(doc, L"sizing");
  tr.Start();
 
  for each (Connector ^connector in cSet)
  {
    if (connector->ConnectorType 
      != ConnectorType::EndConn)
    {
      continue;
    }
 
    connector->Width::set((500 * 0.0032808399));
    connector->Height::set((500 * 0.0032808399));   // This is not set into the drawing
    break;
  }
 
  tr.Commit();
 
  return Result::Succeeded;
}

Here is the second test doing exactly the same thing but using two separate transactions:

  Transaction tr(doc, L"sizing");
  tr.Start();
 
  // We do separate transactions for both dimensions
 
  for each (Connector ^connector in cSet)
  {
    if (connector->ConnectorType 
      != ConnectorType::EndConn)
    {
      continue;
    }
 
    connector->Width::set((500 * 0.0032808399));
    break;
  }
 
  tr.Commit();
 
  tr.Start();
 
  for each (Connector ^connector in cSet)
  {
    if (connector->ConnectorType 
      != ConnectorType::EndConn)
    {
      continue;
    }
 
    connector->Height::set((500 * 0.0032808399));
    break;
  }
 
  tr.Commit();

Answer: I have two suggestions for you, but only one is meant seriously:

You could use automatic regeneration mode. I would not recommend this, however, for many reasons, not least because it is obsolete and will soon be removed.
You could try to regenerate the document between the setting of the two parameters. Does this help?

Response: Thanks for your quick and complete answer.

Yes, regeneration between those settings does help; no whole additional transaction procedure is needed.

Thanks again and best wishes for this New Year 2011!