Read Only Parameter Exception

[StruSoft_Iwona]

I made a code what turns on (enables) analytical models of walls, floors, beams and columns. Its worked very well on my test files. But i have got some older files from my collegue and i always get InvalidOperationException with the message "The parameter is read-only." on those files. What can be the difference? Why is it happening?

[Revitalizer · Accepted solution]

Hi,

a parameter becomes read-only if it is driven by another one.

For example, the user can define a key/value table in which a user parameter drives the "Comments" parameter.

In this case, you cannot set the comment.

In Revit 2017, there are also GlobalParameters which can drive other parameters.

Revitalizer

[Anonymous]

Revitalizer,

Can you further explain this? I'm having the same issue only with Isolated Foundation Elements. I'm trying to collect them and change their workset, but "The parameter is read only" keeps happening when I run my macro. I do not understand why. I posted on the forum last week and haven't heard back. 

	var otherfndCollector = new FilteredElementCollector(doc).OfClass(typeof(FamilyInstance)).OfCategory(BuiltInCategory.OST_StructuralFoundation);
						IList<Element> otherfndcollector1 = otherfndCollector.ToElements();
						
						var otherfndtypeelements = from element in otherfndCollector
							where element.Name.Contains("Pile") || element.Name.Contains("Footing") || element.Name.Contains("PC") || element.Name.Contains("Caisson")
							select element;

Am I collecting them wrong? 

Thank you,

Damien

[Revitalizer]

Hi,

the question is if you get the correct parameter.

If you get it by its plain, localized name, there may be several ones of that name, perhaps some of them hidden to the user.

It may be that one can be set while another one cannot.

I would recommend to investigate the desired elements' parameters by RevitLookup.

So you can find a parameter's related BuiltInParameter (if existing) and get the correct parameter language-independent.

Sometimes parameters are readonly because they are meant to be set in an indirect way, by setting a property or another, connected parameter.

Revitalizer

[Anonymous]

Revitalizer,

Ok so I figured out why I am getting the read only issue. Its because of my pile cap has nested piles inside. If I take the pile cap out, the macro works. The filter is trying to collect the nested piles, and they are the reason the read only is showing up.  How would I go about ignoring the read only or overwriting the read only.

Thank you,

Damien

[jlpgy]

Hi:

I have read this chat and wanna ask one more question:

Is there a general method of querying whether a parameter is read-only or writable?

[naveen.kumar.t]

Hi @jlpgy,

You can find whether the parameter is readonly or not using the below code

if(parameter.IsReadOnly)
                        {
                            //Do something if parameter is readonly
                        }
                        else
                        {
                            //Do something if parameter is writable
                        }

[jlpgy]

@naveen.kumar.t

Hi:

Thank you very much.

I just realized that I asked a silly question, because several minutes after I post the question, I found this property by RevitLookup...

Thanks !

[Anonymous]

He is right. Nested families, stacked walls causes this exception.