Retrieving Classes and Categories from the 'Main Model'

We just got another 5 or 6 inches of snow over the last couple of days.  After the foot or so that we had over Christmas (that quickly melted once it got up to the 60's for a day!) I believe this is probably the most snow we've had this early for quite some time.

I'm working on a material collection project in Revit right now.  Part of this collection hinges on  obtaining a plus-minus report that lists all elements and their properties for each 'option set' in the house.

Revit has a 'DesignOption' field for each element, whether it be a system family or a custom family, that defaults to 'Main Model.'  Once the item is placed into a design option, this is obviously changed to the design option id in the database. Here I get an IList<T> of the walls in the main model:

/*Walls in Main Model*/
BuiltInParameter bip = BuiltInParameter.DESIGN_OPTION_PARAM;
ParameterValueProvider provider = new ParameterValueProvider(new ElementId(bip));
FilterStringRuleEvaluator evaluator = new FilterStringEquals();
FilterRule rule = new FilterStringRule(provider, evaluator, "Main Model", false);
ElementParameterFilter filter = new ElementParameterFilter(rule);


FilteredElementCollector collectorCoreWalls = new 
    FilteredElementCollector(m_doc).OfClass(typeof(Wall)).WherePasses(filter);
IList<Element> coreWalls = collectorCoreWalls.ToElements();

The same can be done for Floors (Floor), Roofs (RoofBase), Ceilings and Floors (CeilingAndFloor) and others.

Next post I'll show how to loop through Design Option Elements.

Retrieving a wall's Function Parameter (BuiltInParameter.FUNCTION_PARAM)

For part of a large Revit material-gathering project I'm working on, I need to retrieve a wall's function. Walls can be assigned six functions from within their type properties:

• Interior
• Exterior
• Foundation
• Retaining
• Soffit
• Core-Shaft

At first I thought it would be fairly straight-forward, and I'd just do this grab the valuestring of the 'FUNCTION_PARAM' like so:

eWall.get_Parameter("Function").AsValueString()

But that gave me a NULL value and crashed Revit. The approach that worked for me was this:

static public string IsExterior(Element e, Document doc)
{
    ElementId id = e.GetTypeId();
    ElementType wallType = doc.get_Element(id) as ElementType;

    Parameter wallFunction = wallType.get_Parameter
        (BuiltInParameter.FUNCTION_PARAM);
    WallFunction value  = (WallFunction)wallFunction.AsInteger();

    return value.ToString();
}

Thanks to Jeremy Tammik's SDK example for setting me straight.