Chicken Spectacular Casserole

3 cups cooked, diced chicken
1 package Uncle Ben's white and wild rice mix -- cooked
1 can cream of celery soup
1 jar sliced pimento
1 medium onion, chopped
1 can French-style green beans, drained
1 cup mayonnaise
1 can water chestnuts, diced
grated cheddar cheese

Heat oven to 350ºF. Mix all ingredients together then pour into buttered 3-quart casserole. Spread grated cheese over top. Bake about 25 to 30 minutes. Serves 8.