Preheat oven to 350 degrees F (175 degrees C). Grease a casserole dish.
In a bowl, stir together the cream of celery soup, sour cream, Cheddar cheese, onion, and salt until well combined. Mix the green beans and corn together in the prepared dish, and spread the soup mixture over the vegetables. Place the crushed crackers in a bowl and stir in the butter. Spread the crumbs over the casserole.
Bake in the preheated oven until the casserole is bubbling and the crumb topping is golden brown, about 45 minutes.