public Result Execute( ExternalCommandData commandData, ref string message, ElementSet elements) { UIApplication app = commandData.Application; Document doc = app.ActiveUIDocument.Document; string familyFilenameFilter = string.Empty; string typeNameFilter = string.Empty; bool caseSensitive = false; IEnumerable <Family> nestedFamilies = NestedFamilyFunctions.GetFilteredNestedFamilyDefinitions( familyFilenameFilter, doc, caseSensitive); foreach (Family f in nestedFamilies) { Debug.WriteLine(f.Name); } List <FamilyInstance> instances = NestedFamilyFunctions.GetFilteredNestedFamilyInstances( familyFilenameFilter, typeNameFilter, doc, caseSensitive); foreach (FamilyInstance fi in instances) { Debug.WriteLine(Util.ElementDescription(fi)); } return(Result.Failed); }