Question

我想在更改其他下拉列表中的所选项目时更新下拉列表的条目。我有三个下拉列表，代表天，月和年我想要的是当我更新月份时我希望日期下拉列表中的日期相应地更改，例如我在月份DDL中选择4（即4月）我想要天DDL显示条目到30岁。这是我已经完成但没有效果

if (ddlmonth.SelectedIndex.Equals(6) || ddlmonth.SelectedIndex.Equals(6) || ddlmonth.SelectedIndex.Equals(9) || ddlmonth.SelectedIndex.Equals(11))
{

    for(int i = 1; i <= 30; i++)
    {
        this.ddldate.Items.Add(i.ToString());
    }
}

我为所有3个DDL启用了自动回发仍然没有效果。在Page_Load上我添加了以下年份和月份供选择。

if (!IsPostBack)
{
    for (int i = 1990; i < 2021; i++)
        this.ddlyear.Items.Add(i.ToString());

    for (int i = 1; i <= 12; i++)
        this.ddlmonth.Items.Add(i.ToString());

}

Answer 1

你应该添加这个函数void Index_Changed（Object sender，EventArgs e） http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.listcontrol.onselectedindexchanged.aspx

Answer 2

这是一些测试代码的东西

Aspx页码

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="Temp._Default" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <title></title>
</head>
<body>
    <form id="form1" runat="server">Year
    <asp:DropDownList ID="_year" runat="server" onselectedindexchanged="_year_SelectedIndexChanged" AutoPostBack="true">
    </asp:DropDownList>Month
    <asp:DropDownList ID="_month" runat="server" onselectedindexchanged="_month_SelectedIndexChanged" AutoPostBack="true">
    </asp:DropDownList>Day
    <asp:DropDownList ID="_day" runat="server" onselectedindexchanged="_day_SelectedIndexChanged" AutoPostBack="true">
    </asp:DropDownList>
    </form>
</body>
</html>

和aspx.cs文件代码是

namespace Temp
{
    public partial class _Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            if (!Page.IsPostBack)
            {
                _year.DataSource = GetData.getYear();
                _year.DataTextField = "Year";
                _year.DataBind();
                _month.Items.Add(new ListItem("Select"));
                _month.DataBind();
                _day.Items.Add(new ListItem("Select"));
                _day.DataBind();
            }
        }
        protected void _year_SelectedIndexChanged(object sender, EventArgs e)
        {
            _month.Items.Clear();
            _month.DataSource = GetData.getMonth();
            _month.DataTextField = "MonthName";
            _month.DataValueField = "MonthId";
            _month.DataBind();
        }
        protected void _month_SelectedIndexChanged(object sender, EventArgs e)
        {
            _day.Items.Clear();
            _day.DataSource = GetData.getDays(_month.SelectedIndex+1,GetData.isLeapYear(Convert.ToInt32(_year.SelectedValue)));
            _day.DataTextField = "Day";
            _day.DataBind();
        }
        protected void _day_SelectedIndexChanged(object sender, EventArgs e)
        {
           //Use selected value of _month _year and _day here
        }
    }    
    public class GetData
    {
        public static List<day> getDays(int monthId,bool isLeapYear)
        {
            int maxLimit;
            if (monthId == 2)
            {
                if (isLeapYear) maxLimit = 29;
                else maxLimit = 28;
            }
            else if (monthId == 1 || monthId == 3 || monthId == 5 || monthId == 7 || monthId == 8 || monthId == 10 || monthId == 12)
                maxLimit = 31;
            else maxLimit = 30;
            List<day> days = new List<day>();
            for (int i = 1; i <= maxLimit; i++)
            {
                days.Add(new day { Day = i });
            }
            return days;

        }
        public static List<year> getYear()
        {
            //Set here min and max range of year 
            int minLimit = 1950;
            int maxLimit = DateTime.Now.Year;
            List<year> years = new List<year>();
            for (int i = minLimit; i <= maxLimit; i++)
            {
                //You can modify code for bind year dropdown 
                //respectively change in date or month
                /*if (isLeapYear)
                {
                    if(i%4==0)
                        years.Add(new year { Year = i });
                }
                else*/
                years.Add(new year { Year = i });
            }
            return years;
        }
        public static List<month> getMonth()
        {
            List<month> months=new List<month>();            
            months.Add(new month { MonthId = 1, MonthName = "Jan" });
            months.Add(new month { MonthId = 2, MonthName = "Frb" }); months.Add(new month { MonthId = 3, MonthName = "Mar" });
            months.Add(new month { MonthId = 4, MonthName = "Apr" }); months.Add(new month { MonthId = 5, MonthName = "May" });
            months.Add(new month { MonthId = 6, MonthName = "Jun" }); months.Add(new month { MonthId = 7, MonthName = "July" }); 
            months.Add(new month { MonthId = 8, MonthName = "Aug" });
            months.Add(new month { MonthId = 9, MonthName = "Sep" }); months.Add(new month { MonthId = 10, MonthName = "Oct" });
            months.Add(new month { MonthId = 11, MonthName = "Nov" });months.Add(new month { MonthId = 12, MonthName = "Dec" });
            return months;
        }
        internal static bool isLeapYear(int p)
        {
            if (p % 4 == 0)
                return true;
            else return false;
        }
    }
    public class month
    {
        public string MonthName { get; set; }
        public int MonthId { get; set; }
    }
    public class day
    {
        public int Day { get; set; }
    }
    public class year
    {
        public int Year { get; set; }
    }
}

通过从其他下拉列表中选择来更新下拉列表项

2 个答案: