I hate when people do that. Anyway, here's what I found out, for anyone else who hasn't heard of Dogfest before:
It's held at Charles County Fairground; just south of La Plata. It's 2 days of lots of dog related exhibits and demonstrations. There's live entertainment, seminars about dogs, dog agility demonstrations and everything dog related. You will find the adoption and rescue groups there - I'd imagine they'll even have some dogs there to adopt. (You might want to find out if your favorite rescue is going to be there and get pre-screened for a dog, if you want to take one home with you).
It's family and dog friendly, so long as your dog is leashed. No admission fee is mentioned in the flyer; don't know if there are food and drink vendors there or not. Maybe someone else knows more about that. Sounds like it could be a lot of fun, but not sure since I'm just reading the flyer rather than reading about someone's experience with the event.