passing selected values from dropdown to service parameter . . .

Hi there -

We're on Thingworx 8.5.15.  I have a mashup that contains a dropdown widget.  I have a service that is used to populate the available choices for the dropdown.  I want to pass the selected values (plural) of the dropdown as a parameter to a second service for processing.  The second service takes a parameter of type String.  In this thread, @Ashritha states that it's a simple matter of binding the Selected Rows property of the first service as a parameter to the second service.  When I try this and log the parameter values received by the second service, I find that it only receives a single String value for processing.

What must be done in order to pass multiple values to a service parameter and receive multiple values as a service parameter?

thanks in advance,

dgg