private static void ReverseArray(int[] array)
        {      
            int temp;
            int count = array.Length;
            for (int i = 0; i < count/2; i++)
            {
                temp = array[count - 1 - i];
                array[count - 1 - i] = array[i];
                array[i] = temp;
            }     
        }

//Test

            int[] oldArray = new int[] { 3, 4, 6, 7, 33, 56, 5, 12, 100 };
            Console.WriteLine("Before reverse:");
            foreach (int element in oldArray)
            {
                Console.Write(element + ",");
            }

            ReverseArray(oldArray);

            Console.WriteLine();
            Console.WriteLine("After reverse:");
            foreach (int element in oldArray)
            {
                Console.Write(element + ",");
            }
            Console.ReadLine();