Preheat oven to 350 degrees. Combine cake mix, mandarin oranges, eggs and oil. Beat 2 minutes on highest speed then reduce speed to lowest setting and and beat for 1 minute. Pour batter into 3 greased and floured 9-inch round cake pans. Bake at 350 degrees for 25 minutes. Cool in pans for 10 minutes, remove layers and cool completely. Combine Cool Whip, dry pie filling and pineapple. Beat for 2 minutes at medium speed. Let stand 5 minutes or until mixture is to spreading consistency. Spread pineapple mixture between layers and on top and sides of cake. Chill for at least 2 hours before serving. Store in refrigerator.