BoxAndUnbox

 class Program
    {
        // 值类型的反向转换，就是一个unbox，
        static void Main(string[] args)
        {
            int totalCount;
            ArrayList list = new ArrayList();

            Console.WriteLine("Enter a number between 2 and 1000:");
            totalCount = int.Parse(Console.ReadLine());
            
            list.Add((double)0);// box，从 0 封装成double，再转换成一个object对象
            list.Add((double)1);// box，从 0 封装成double，再转换成一个object对象

            for (int count = 2; count < totalCount; count++)
            {
                list.Add((double)list[count - 1] + (double)list[count - 2]);// 2 unbox+1 box，把Object类型的数转换成double类型的数，再进行相加，最后在转换成object类型
            }

            foreach (double count in list)// unbox，从Object类型转换成double类型。
            {
                Console.Write("{0,5}",count);// box，从double类型转换成Object类型。
            }
            Console.WriteLine();
            Console.WriteLine("----------------------------------------------------");

            int number;
            object thing;
            double bigNumber;

            number = 42;
            thing = number;

            try
            {
                bigNumber = (double)(int)thing;
                Console.WriteLine(bigNumber);

            }
            catch (InvalidCastException exception)
            {
                Console.WriteLine("异常信息：{0},The Log is {1}",exception.Message,exception.Source);
            }
        }
    }