//取得内参名称
[Transaction(TransactionMode.Manual)]
[Regeneration(RegenerationOption.Manual)]
public class cmdGetBuiltInParam : IExternalCommand
{
    public Result Execute(ExternalCommandData cmdData, ref string msg, ElementSet elements)
    {
        UIDocument uiDoc = cmdData.Application.ActiveUIDocument;
        Document doc = uiDoc.Document;
        Selection sel = uiDoc.Selection;

        Duct duct = doc.GetElement(sel.PickObject(ObjectType.Element, "选择")) as Duct;
        foreach (Parameter p in duct.Parameters)
        {
            if (p.Definition.Name == "高度")
            {
                BuiltInParameter biParam = (BuiltInParameter)p.Id.IntegerValue;
                TaskDialog.Show("builtIn", biParam.ToString());
            }
        }

        return Result.Succeeded;
    }
}