I know it is not a good netiquette to answer a question with a question but why do you want to bind to a String? I don’t know if it is even possible as String is immutable (and is definitely no Java Bean). And why bind to it? You can get the String with comboBox.getValue().
Yep, I know about the string immutability and I know I could read the value from the component or use VCL:s to update the String etc, I was just curious in general if you could use the same semantics for all binding…