新手问两个关于DropDownList的问题

Question

1、用DropDownList 录入生日，应该怎么做，要是闰年，还要注意2月。。
2、我用两个DropDownList  ，前一个里有A、B两项，后一个里有1 2 3 4 ，当我选A的时候，后一个只显示1 2 。。拜谢 求解答 

Answer 1

第一个问题吧，找个相关js吧
第二个好像可以用selectedindexchnge事件

Answer 2

页面上有三个DropDownList 年月日if (!IsPostBack)
                Bind();
            }private void Bind()
        {
         
            DateTime now = DateTime.Today;            this.drpYear.Items.Clear();
            this.drpMonth.Items.Clear();
            this.drpMonth.Items.Clear();            for (int i = 0; i < 70; i++)
            { 
              this.drpYear.Items.Add(new ListItem((now.Year-i).ToString(),(now.Year-i).ToString()));
            }            for(int i=1;i<=12;i++)
            {
              this.drpMonth.Items.Add(new ListItem(i.ToString(),i.ToString()));
            }            int day = DateTime.DaysInMonth(now.Year,now.Month);            for(int i=1;i<=day;i++)
            {
              this.drpDay.Items.Add(new ListItem(i.ToString(),i.ToString()));
            }            this.drpYear.SelectedValue=now.Year.ToString();
            this.drpMonth.SelectedValue=now.Month.ToString();
            this.drpMonth.SelectedValue=now.Day.ToString();        }        private void ChangeYearOrMonth()
        {
            int year =  int.Parse(this.drpYear.SelectedValue);
            int month =  int.Parse(this.drpMonth.SelectedValue);            int day = DateTime.DaysInMonth(year, month);//这里根据年，月，得到月的天数            this.drpDay.Items.Clear();
            for (int i = 1; i <=day; i++)
            {
                this.drpDay.Items.Add(new ListItem(i.ToString(), i.ToString()));
            }
        
        } protected void drpYear_SelectedIndexChanged(object sender, EventArgs e)
        {
            ChangeYearOrMonth();
        }        protected void drpMonth_SelectedIndexChanged(object sender, EventArgs e)
        {
            ChangeYearOrMonth();
        }