I would like to point out that we rotate left when the shifting value is negative and we rotate right when the value is positive.
    public static void Main()
    {
        int[] array = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
        int shiftCount = 1;
        Rotate(ref array, shiftCount);
    ...