How to make a button inactive if input field is empty?

There is a dropdown input field and a save button on a page. How can I make it so that the save button would be inactive (different color and not clickable) if nothing is selected in the dropdown?
1 answers

You could use an expression for visibility.  Have 2 buttons – one a save button and one a button that doesn’t do anything (with a caption of Save).  In the visibility expression for each one, set one to be visible when the field is empty and one to visible when it is not empty.