高效字符串逆转

        public static string Reverse(this String str)
        {
            char[] array = str.ToCharArray();
            int n = array.Length - 1;
            for (int i = (n - 1) >> 1; i >= 0; i--)
            {
                int j = n - i;
                char temp = array[i];
                array[i] = array[j];
                array[j] = temp;
            }
            return new string(array);
        }