Cunningham leads the league with 17 goals this season and his latest one kept alive his team's hopes for a playoff berth.
San Jose (7-13-7) was eliminated from playoff contention.
It was the fourth win in five games for Dallas (10-12-6), which took the lead in the fifth minute on a goal by David Ferreira.
San Jose tied it on Quincy Amarikwa's goal in the 73rd minute.
Copyright 2009 by United Press International.