Hi
Try to use ParameterFilterUtilities
List<ElementId> catList = new List<ElementId>(); catList.Add(doc.Settings.Categories.get_Item(BuiltInCategory.OST_Windows).Id); catList.Add(doc.Settings.Categories.get_Item(BuiltInCategory.OST_Doors).Id); List<ElementId> paramList = ParameterFilterUtilities.GetFilterableParametersInCommon(doc, catList).ToList();
This link will help you