*Cook beans if needed.
*in a small bowl, add sweet corn and cover with warm water. Let sit 5-10 minutes or until corn is softened and rehydrated. Drain.
*Mix black beans, pinto beans, corn, green chiles, red onion and cilantro together in a large bowl.
*To make the dressing, stir the vinegar, vegetable oil, and sugar together in a pan. Bring to a boil, then remove from heat, and cool. Pour dressing over bean mixture, and toss to coat evenly.