How to retrieve Parameter Value of a Family Element ?

[huiput2006707889]

I have been try to get the parameter value of family

public class Trial : IExternalCommand
{
public Result Execute(ExternalCommandData commandData, ref string message, ElementSet elements)
{
UIApplication uiApp = commandData.Application;
Document doc = uiApp.ActiveUIDocument.Document;

ElementCategoryFilter Family = new ElementCategoryFilter(BuiltInCategory.OST_StructuralFoundation);
FilteredElementCollector collector = new FilteredElementCollector(doc);
IList<Element> Familylist = collector.WherePasses(Family).ToElements();
String prompt = "The Precast Element in the current document are:\n";
foreach (Element e in Familylist)
{
Parameter p = e.get_Parameter(BuiltInParameter.FAMILY_BASE_LEVEL_PARAM);
string levelshow = string.Format("Base Level", p.AsValueString());

prompt += levelshow + "\n";

}
TaskDialog.Show("Revit",prompt);
return Result.Succeeded;
}

}

when i run this add-ins in revit, it doesn't work。 But i cant spot any problem

[david_peterson]

Not an API solution, but I've used an Add-In Schedule creator that you can get to return basically any object parameter via a schedule.

[peterjegan]

When you filter for elements by Built-In Category, you get Elements and ElementTypes of the category. If you then try to get an instance-based parameter (like "Base Level") the types don't have it, and your code fails.

Try changing this line:

IList<Element> Familylist = collector.WherePasses(Family).ToElements();

To:

IList<Element> Familylist = collector.WherePasses(Family).WhereElementIsNotElementType().ToElements();