新加载的Revit API系列中的GetFamilySymbolsId为null

Question

I'm curious the results of the code snip below. I want to grab a family by name and insert the very first symbol found in that family.

This works fine for families with multiple symbols. However, for those with no specific type definitions, sometimes symId.Count() = 1 and other times, a null exception is returned. Why is this the case?

  Element el1 = new FilteredElementCollector(doc).OfClass(typeof(Autodesk.Revit.DB.Family)).FirstOrDefault(x => x.Name == familyName);

                Autodesk.Revit.DB.Family fam = el1 as Autodesk.Revit.DB.Family;

                ISet<ElementId> symIds = fam.GetFamilySymbolIds();

                foreach (ElementId elid in symIds)
                {
                    FamilySymbol symbol = doc.GetElement(elid) as FamilySymbol;
                    try
                    {
                        uidoc.PromptForFamilyInstancePlacement(symbol);
                    }
                    catch { }
                    break;
                }

Interesting follow up. When I go into the base family, add some types, delete fom project, and reload - I get the same error.

Answer 1

You say, 'sometimes a null exception is returned'.

That is rather unspecific.

I suggest you debug the code step by step and determine exactly which API call is throwing the exception, and exactly what the exception message says.

That will probably clarify what is going on.