aspx页面上有三个DropDownList控件，
DropDownList1 表示年，DropDownList2表示月，DropDownList3表示天；
注意用将这三个DropDownList控件的AutoPostBack属性设为True。
用户可以方便地选择年月日，并且每月的日期会随着用户选择不同的年，月而发生相应的变化
其后台cs文件代码如下：
private void Page_Load(object sender, System.EventArgs e)
{
DateTime tnow=DateTime.Now;//现在时间
ArrayList
AlYear=new ArrayList();
int i;
for(i=2002;i
AlYear.Add(i);
ArrayList
AlMonth=new ArrayList();
for(i=1;i
AlMonth.Add(i);
if(!this.IsPostBack )
{
DropDownList1.DataSource=AlYear;
DropDownList1.DataBind();//绑定年
//选择当前年
DropDownList1.SelectedValue=tnow.Year.ToString();
DropDownList2.DataSource=AlMonth;
DropDownList2.DataBind();//绑定月
//选择当前月
DropDownList2.SelectedValue=tnow.Month.ToString();
int year,month;
year=Int32.Parse(DropDownList1.SelectedValue);
month=Int32.Parse(DropDownList2.SelectedValue);
BindDays(year,month);//绑定天
//选择当前日期
DropDownList3.SelectedValue=tnow.Day.ToString();
}
}
//判断闰年
private bool CheckLeap(int year)
{
if((year%4==0)&&(year%100!=0)||(year%400==0))
return true;
else return false;
}
//绑定每月的天数
private void BindDays( int year,int month)
{
int i;
ArrayList
AlDay=new ArrayList();
switch(month)
{
case 1:
case 3:
case 5:
case 7:
case 8:
case 10:
case 12:
for(i=1;i
AlDay.Add(i);
break;
case 2:
if (CheckLeap(year))
{for(i=1;i
AlDay.Add(i);}
else
{for(i=1;i
AlDay.Add(i);}
break;
case 4:
case 6:
case 9:
case 11:
for(i=1;i
AlDay.Add(i);
break;
}
DropDownList3.DataSource=AlDay;
DropDownList3.DataBind();
}
//选择年
private void DropDownList1_SelectedIndexChanged(object sender, System.EventArgs e)
{
int year,month;
year=Int32.Parse(DropDownList1.SelectedValue);
month=Int32.Parse(DropDownList2.SelectedValue);
BindDays(year,month);
}
//选择月
private void DropDownList2_SelectedIndexChanged(object sender, System.EventArgs e)
{
int year,month;
year=Int32.Parse(DropDownList1.SelectedValue);
month=Int32.Parse(DropDownList2.SelectedValue);
BindDays(year,month);
}