If I have a long choice list and I'd like the user to be able to 'search' the choices. This is in part possible with the 'Allow Fill in' option, as it shows choices as you type. However, this allows the user to enter a value which is not in the choice list which is not desirable.
Can this be achieved?
Is there a custom error which can be used to validate the field has a choice from the choices in the list?