Retrieving the Electrical Load from a Fixture

Today is my birthday, so I am trying hard to work less.

I am not completely successful, though, I'm afraid.

Very kindly, Alexander @aignatovich @CADBIMDeveloper Ignatovich, aka Александр Игнатович, provided us all with a gift for the day in the form of a new external command CmdElectricalLoad that he submitted to The Building Coder samples in pull request #12, saying:

I recently answered a question on the Russian ADN forum on how to retrieve the value from the Load column in the electrical system browser for a specific fixture family instance, активная электрическая мощность элемента (in English, active electric power of an element):

Question: Tell me how to get the built-in parameter of the active power of an element in the category of electrical appliances OST_ElectricalFixtures.

RevitLookup provides information only on electrical circuits.

I am searching for the value of the power parameter, but it is not visible in the element. If you go into ElectricalSystem, it starts working with circuits, and I need the power of the elements.

Answer: First, you need to get the necessary connector from the family related to the system of interest:

  var mepConnectorInfo = connector.GetMEPConnectorInfo();

From that, we can get the value of the ParameterValue parameter:

  var parameterValue
    = ( DoubleParameterValue ) mepConnectorInfo
      .GetConnectorParameterValue ( new ElementId (
        BuiltInParameter . RBS_ELEC_APPARENT_LOAD ) );

And the final step:

  var value = UnitUtils.ConvertFromInternalUnits(
    parameterValue.Value, DisplayUnitType.DUT_WATTS );

Thank you very much, Alexander, for answering this important question and sharing the solution in such a useful form!

I edited Alexander's new command and added it to the text file BcSamples.txt for loading it using the Revit SDK RvtSamples application∫®. 

Here is the resulting code, including Alexander's inimitable use of advanced .NET functionality enabling extremely succinct code:

CmdElectricalLoad

  [Transaction( TransactionMode.Manual )]
  public class CmdElectricalLoad : IExternalCommand
  {
    class ElectricalApparentLoad
    {
      public ElectricalApparentLoad( 
        ElectricalSystemType electricalSystemType, 
        int connectorId, 
        double apparentLoad )
      {
        ElectricalSystemType = electricalSystemType;
        ConnectorId = connectorId;
        ApparentLoad = apparentLoad;
      }

      public ElectricalSystemType ElectricalSystemType { get; }

      public int ConnectorId { get; }

      public double ApparentLoad { get; }

      public override string ToString() => 
        $"{ElectricalSystemType}: {ConnectorId} "
        + "- {ApparentLoad} V*A";
    }

    class ElectricalApparentLoadFactory
    {
      public IEnumerable<ElectricalApparentLoad> 
        Create( FamilyInstance familyInstance )
      {
        return familyInstance.MEPModel
          .ConnectorManager
          .Connectors
          .Cast<Connector>()
          .Select( Create )
          .Where( x => x != null );
      }

      private static ElectricalApparentLoad Create( 
        Connector connector )
      {
        if( connector.Domain != Domain.DomainElectrical )
          return null;

        var mepConnectorInfo 
          = connector.GetMEPConnectorInfo() 
            as MEPFamilyConnectorInfo;

        var parameterValue = mepConnectorInfo
          ?.GetConnectorParameterValue( 
            new ElementId( 
              BuiltInParameter.RBS_ELEC_APPARENT_LOAD ) )
                as DoubleParameterValue;

        if( parameterValue == null )
          return null;

        var load = UnitUtils.ConvertFromInternalUnits( 
          parameterValue.Value,
          DisplayUnitType.DUT_VOLT_AMPERES );

        return new ElectricalApparentLoad( 
          connector.ElectricalSystemType, 
          connector.Id, load );
      }
    }

    class FamilyInstanceWithApparentLoadSelectionFilter 
      : ISelectionFilter
    {
      private readonly ElectricalApparentLoadFactory 
        electricalApparentLoadFactory;

      public FamilyInstanceWithApparentLoadSelectionFilter( 
        ElectricalApparentLoadFactory 
          electricalApparentLoadFactory )
      {
        this.electricalApparentLoadFactory 
          = electricalApparentLoadFactory;
      }

      public bool AllowElement( Element elem )
      {
        var familyInstance = elem as FamilyInstance;

        if( familyInstance == null )
          return false;

        return electricalApparentLoadFactory
          .Create( familyInstance )
          .Any();
      }

      public bool AllowReference( Reference r, XYZ p ) 
        => false;
    }

    public Result Execute( 
      ExternalCommandData commandData, 
      ref string message, 
      ElementSet elements )
    {
      var app = commandData.Application;
      var uidoc = app.ActiveUIDocument;

      var familyInstance 
        = SelectFamilyInstanceWithApparentLoad( 
          uidoc );

      if( familyInstance == null )
        return Result.Cancelled;

      var electricalApparentLoadFactory 
        = new ElectricalApparentLoadFactory();

      var apparentLoads = electricalApparentLoadFactory
        .Create( familyInstance );

      TaskDialog.Show( "CmdElectricalLoad", 
        string.Join( "\n", apparentLoads ) );

      return Result.Succeeded;
    }

    private static FamilyInstance 
      SelectFamilyInstanceWithApparentLoad( 
        UIDocument uidoc )
    {
      var electricalApparentLoadFactory 
        = new ElectricalApparentLoadFactory();

      var selectionFilter 
        = new FamilyInstanceWithApparentLoadSelectionFilter( 
          electricalApparentLoadFactory );

      try
      {
        return (FamilyInstance) uidoc.Document.GetElement( 
          uidoc.Selection.PickObject( ObjectType.Element, 
            selectionFilter ) );
      }
      catch( OperationCanceledException )
      {
        return null;
      }
    }
  }