Finding Blank Parameters

I have a Revit file i inherited. I want to make a list of all objects where parameter 1 is empty. See my efforts below. Any ideas why it’s not working

There is a space between your two quotes, so rather than comparing your parameter value to an empty string, it is currently being compared to a single whitespace character. In other words, your code block is this:

" ";

but it should be this:


Thanks for your reply. When I remove the space I get all the items that are not blank

I got this to work by wiring out of the in part of list by boolmask node. I’m not sure why it worked. It would be great if somebody could explain.

My problem now is that I want to set a parameter from this list. But the set parameter node needs an element. How do I get the list of elements from my new list

The List.FilterByBoolMask node has two outputs, IN (true) and OUT (false). In order to get the actual elements, you just need to connect your All Elements of Category node to a List.FilterByBoolMask node using the same mask.