public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        //枚举类型
        enum Season
        {
            spring=1,summer,fall,autumn=fall,winter
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            Season k = Season.summer;
            MessageBox.Show(k.ToString());

            object o = k;
            int? i = 9;
            i = o as int?;
            if (o == null)
            {
                MessageBox.Show("fail");
            }
            else
            {
                MessageBox.Show(i.ToString());
            }

            //int i = (int)k;
            //MessageBox.Show(i.ToString());
            
        }
    }