Find Prime factors of the given natural number

class EncodeNumber
    {
        public EncodeNumber()
        {
            int n = -18;

            int[] result = encodeNumber(n);
            Console.WriteLine("The return array of encode number {0} is", n);
            if(result!=null)
                foreach (int temp in result)
                    Console.Write(temp + "\t");
        }

        int[] encodeNumber(int n)
        {
            if (n <= 1)
                return null;
            //int num = 1;
            int nnew = n;
            List<int> arr = new List<int>();

            while(nnew>1)
            {
                //num = 1;
                for (int i = 2; i <= nnew; i++)
                {
                    if (nnew % i == 0 && isPrime(i))
                    {
                        arr.Add(i);
                        //num = num * i;
                        nnew = nnew / i;
                        break;
                    }

                }
                //nnew = nnew / num;
            }
            return arr.ToArray();
        }

        Boolean isPrime(int x)
        {
            bool status = true;
            for (int i = 2; i <= x / 2; i++)
            {
                if (x % i == 0)
                {
                    status = false;
                    break;
                }
            }
            return status;
        }
    }