Harrisonburg is an independent city. I would recommend using the wiki for Richmond (another independent city) as an example. Independent cities in VA combine the functions of a city and a county.
Harrisonburg is in Rockingham county if that helps but is, as Fredva said, an independent city. If its about the Provoice system then that covers the city and county from the look of the DB.
Sorry, that was me. I am new to adding information to the wiki. I created information for Rockingham County, and linked it under Harrisonburg/ Rockingham's TRS. The information was then moved to a new page for Rockingham. I tried to follow that example for Harrisonburg... I'll take a look when I have a little more time.