Chapter 4. WinForm（ComboBox控件--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.Windows.Forms;

namespace 日期选择器
{
    public partial class 日期选择器 : Form
    {
        public 日期选择器()
        {
            InitializeComponent();
        }

        private void 日期选择器_Load(object sender, EventArgs e)
        {
            //程序加载的时候将年份添加到下拉框中
            //获得当前年份
            int year = DateTime.Now.Year;
            for (int i = year; i >= 1949; i--)
            {
               cboYear.Items.Add(i+"年");
            }
                
        }

        /// <summary>
        /// 当年份发生改变的时候加载月份
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void cboYear_SelectedIndexChanged(object sender, EventArgs e)
        {
            //添加之前应该清空之前的内容
            cboMonth.Items.Clear();
            for (int i = 1; i <= 12; i++)
            {
                cboMonth.Items.Add(i+"月");
            }
        }

        /// <summary>
        /// 当月份改变的时候添加日期
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void cboMonth_SelectedIndexChanged(object sender, EventArgs e)
        {
            //选择前先清空
            cboDay.Items.Clear();
            //定义一个变量存储天数
            int day=0;
             //获得月份
            string strMonth = cboMonth.SelectedItem.ToString().Split(new char[] { '月' }, StringSplitOptions.RemoveEmptyEntries)[0];
            string strYear = cboYear.SelectedItem.ToString().Split(new char[] { '年' }, StringSplitOptions.RemoveEmptyEntries)[0];
            //MessageBox.Show(cboMonth.SelectedItem.ToString());
            int year = Convert.ToInt32(strYear);
            int month = Convert.ToInt32(strMonth);
            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++)
            {
                cboDay.Items.Add(i + "日");
            }
        }
    }
}