Write a C# method to discover the difference between two arrays. Assume you are given two integer arrays, say a1 and a2, suppose they contain no duplicates. Your method should find the items from a1, which are not included in a2. The resulting array collection must be returned to the caller. Example. Let a1 and a2 be as follows, int[] a1 = { 55, 33, 11 }; and int[] a2 = { 22, 33, 55, 44, 66, 88, 99 }. The returned array should be int[] a3 = { 11 };

Your method must NOT print anything (do not use Console.WriteLine() ). Your method's header is

private static int[] ArrayDifference (int[] a1, int[] a2)