Duct size , Built-Parrameter ( MEP ),

Hi Everyone .
I been trying to modify duct sizes selected by user. I been observing some how strange behavior that I can not find an explanation for !.
The following picture describes a property of a selected duct, and I want to change the following built-in parameters:“Height"Width” and “Lining Thickness”

I tired to solve this problem at “API” level. but still i got unpredictable result. Please see the following code, first bit of code is not predictable and I get an error from Revit ,


Is this something to do with Builtin parameter ?
I can write : “duct.get_Parameter(BuiltInParameter.RBS_CURVE_HEIGHT_PARAM);” but it seems there is no set function available. I appreciate if anyone can help

I also get unpredictable answer in dynamo. it seems the value of built-in parameter is not changing.
Please see the following picture :

Hi @alex.tohid

Can you check if the parameter Is read-only?

Could u upload image with LiningThickness declaration?

I was just getting the thickness from the user , using windows form .

I figured out what was the problem , it got to do with units incompatibility between Revit and my form .
I had to convert the units to match revit.
Thanks everyone