List Box Interface tool, Error Message

Question

Hi Everyone,

I have a problem with my analytic app, because I want to show an error message when the user do not select anything from the ListBox tool, but I don't know how to do it.
I thought the Error Message tool will help me out with this expression: "IsEmpty([#1])". But do not really work.

Is there any way to display an error message when the user do not select anything from the Listbox tool?

Thank you in advance for your help.

Screenshot 2025-05-23 091222.png

alexnajm · Accepted Answer

Very interesting - try this! !Regex_match([#1],"[a-zA-Z]")

It just says if there is not a letter in the selection

Dhrish · Accepted Answer

You can use this expression: Regex_CountMatches([#1],"True")<1.

This counts the number of the checkboxes selected i.e. True. If no checkboxes are selected then the value will be 0 and hence error message will pop-up.