BinarySearch C#

namespace SearchSort
{
    internal class Program
    {
        public static int BinarySearch(int[] arr, int query, int left, int right)
        {
            if (left == right)
            {
                if (arr[right] == query)
                    return left;
                else
                    return -1;
            }

            int middle = (left + right) / 2;
            if (query <= arr[middle])
                return BinarySearch(arr, query, left, middle);
            else
                return BinarySearch(arr, query, middle + 1, right);
        }

        static void Main(string[] args)
        {
            var ints = new int[] { 1, 3, 5, 7, 9 };
            Console.WriteLine(BinarySearch(ints, 7, 0, ints.Length - 1));
        }
    }
}