1) In a small bowl whisk together the lemon juice, salt, pepper and olive oil. Set aside.
2) Put the endive and apples into a large decorative serving bowl. Squeeze the juice of half a lemon into the bowl and toss to coat the endive and apples so they don't turn brown. Add the cheese and avocado, and then add the cranberries and corn.
3) Pour the dressing over the salad just before serving and toss to coat.