用户注册表中日期输入的解决方案

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;

public partial class Default3 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            for (int i = 1900; i <= 2100; i++)
            {
                this.DropDownList1.Items.Add(i.ToString());
            }
            for (int j = 1; j <= 12; j++)
            {
                this.DropDownList2.Items.Add(j.ToString());
            }
            FillDay();
        }
    }
    protected int getDays()
    {
        int year = Convert.ToInt32(this.DropDownList1.SelectedValue);
        int month = Convert.ToInt32(this.DropDownList2.SelectedValue);
        int days = 0;
        //下面是得到当月的天数。。。
        switch (month)
        {
            case 1:
                days = 31; break;
            case 2:
                if (DateTime.IsLeapYear(year))
                {
                    //闰年二月为29天
                    days = 29;
                }
                else
                {
                    //非闰年是28天哟。。
                    days = 28;
                }
                break;
            case 3:
                days = 31; break;
            case 4:
                days = 30; break;
            case 5:
                days = 31; break;
            case 6:
                days = 30; break;
            case 7:
                days = 31; break;
            case 8:
                days = 31; break;
            case 9:
                days = 30; break;
            case 10:
                days = 31; break;
            case 11:
                days = 30; break;
            case 12:
                days = 31; break;
        }
        return days;
    }
    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {
        FillDay();
    }
    protected void FillDay()
    {
        int days;
        DropDownList3.Items.Clear();
        days = getDays();
        for (int day = 1; day <= days; day++)
        {
            this.DropDownList3.Items.Add(day.ToString());
        }
    }
    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        FillDay();
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        this.Label1.Text = "你选择的日期是：" + DropDownList1.SelectedValue+"年"+ DropDownList2.SelectedValue+"月"+ DropDownList3.SelectedValue+"日";
    }
}