日期选择器

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace DateSelect
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void comboBox1_SelectedValueChanged(object sender, EventArgs e)
        {
            monthbox.Items.Clear();
           for (int i=1;i<=12;i++)
            {
                monthbox.Items.Add(i+"月");
            }
          
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            int year = DateTime.Now.Year;
            for (int i = year; i>1949;i--)
            {
                yearbox.Items.Add(i + "年");
            }
        }

        private void monthbox_SelectedValueChanged(object sender, EventArgs e)
        {
            daybox.Items.Clear();
            int day = 0;
            int year =Convert.ToInt32( yearbox.SelectedItem.ToString().Split(new char[] { '年' },StringSplitOptions.RemoveEmptyEntries)[0]);
            int month = Convert.ToInt32(monthbox.SelectedItem.ToString().Split(new char[] { '月' }, StringSplitOptions.RemoveEmptyEntries)[0]);
            switch (month)
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:
                    day = 31;
                    break;
                case 2:
                    if ((year%400==0)||(year%4==0&&year%100!=0))
                    {
                        day = 29;
                    }
                    else
                    {
                        day = 28;
                    }
                    break;
                default:
                    day = 30;
                    break;
            }

            for (int i=1;i<=day;i++)
            {
                daybox.Items.Add(i);
            }
        }
    }
}