与取得元素变量的内参名称类别有个BuiltInParameter
//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;
    }
}url:http://greatverve.cnb
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