Shrimp Corn Casserole

3 T. butter
3 T. flour
1 ½ c. milk
¾ c. cheese
2 cans whole kernel corn, drained
1 T. grated onion
½ tsp. celery seed
¼ tsp. onion salt
1 lb. shrimp

Melt the butter. Stir in the flour and cheese. Stir until melted. Add rest of ingredients and bake at 350°F for 30 minutes. Garnish with parsley.