The two sides traded second half goals within minutes of one another as Homegrown midfielder Kellyn Acosta scored his first MLS goal on the night before Castillo found the game winner in stoppage-time.
FC Dallas got one good chance early from Acosta. In the 9th minute, Michael Barrios drive into the penalty box on a quick counter attack, as he played the ball into the box a DCU defender tapped it away but only as far out to the feet of Acosta who ripped a one-time shot that would be saved by keeper Andrew Dykstra for a corner kick.
Castillo nearly found a breakthrough right before halftime in the 43rd minute as Acosta would send a great ball to the back post where Castillo was all alone on Dykstra but the DCU keeper would pry away the attempt from Castillo at his near post.
United would get their chance on goal in the 59th minute as Jairo Arrieta would steal the ball from Zach Loyd on the end line. He would then take it into the penalty box where Dan Kennedy would make sure to stop his attempt on goal.
Dallas would respond in the 65th minute on a cross from Hollingshead into the penalty box to Harris, who's header would bang off the cross bar and go back out into play where United would clear it from danger.
Dallas would finally make a breakthrough in the 73rd minute as Barrios would whip in a cross to Texeira. The Dallas forward would take one crack on goal that would get blocked out to Acsota, who would score the game's first goal with a one-time shot.
United would get one back just minutes later in the 77th minute on a quick counter attack as Taylor Kemp sent in a hard cross into the penalty box where Arrieta was looking to finish it home. Unfortunately for Dallas the ball would hit off Matt Hedges' right foot and into the goal. The goal ended FC Dallas' shutout streak at 348 minutes.
Castillo would put FC Dallas back up in stoppage time for his eighth goal of the season. Tesho Akindele would send in a cross to Ulloa, who would one time a shot that would get deflected to Castillo at the top of the six-yard box. The Colombian made sure to hammer home the shot to give Dallas the three points.
FC Dallas returns to action next week as they host western rivals Portland.