在編程中選中某項的方法：
DropDownList1.ClearSelection();
DropDownList1.Items.FindByValue(st.Year.ToString()).Selected = true;
如果不清空選中項的話(huà)，會(huì )出現：不能在 DropDownList 中選擇多個(gè)項。
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
int year = int.Parse(DropDownList1.SelectedValue);
int month = int.Parse(DropDownList2.SelectedValue);
int day = DateTime.DaysInMonth(year, month);
DropDownList3.Items.Clear();
for (int i = 1; i <= day; i++)
{
ListItem newItem = new ListItem(i.ToString(), i.ToString());
DropDownList3.Items.Add(newItem);
}
}
不過(guò)我遇到的不是這個(gè)問(wèn)題，是個(gè)Bug，關(guān)機再開(kāi)就能運行，奇怪。而且VS2005IDE鍵位還變了，刪除行變成了Ctrl+Y(VB的習慣)，恢復預置環(huán)境就好了。
看來(lái)遇到問(wèn)題還是要冷靜：可以采用的處理方法是：祈禱一句，罵一句，睡一覺(jué)，關(guān)機一次。
下面附一個(gè)最基本的實(shí)例。主要，要實(shí)現聯(lián)動(dòng)DropDownList1的AutoPostBack屬性要開(kāi)。
Default.aspx
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_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>無(wú)標題頁(yè)</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:DropDownList ID="DropDownList1" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="DropDownList2" runat="server" AutoPostBack="True" OnSelectedIndexChanged="DropDownList1_SelectedIndexChanged">
</asp:DropDownList>
<asp:DropDownList ID="DropDownList3" runat="server">
</asp:DropDownList></div>
</form>
</body>
</html>
Default.aspx.cs
using System;
using System.Data;
using System.Configuration;
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 _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack == false)
{
for (int i = 2001; i < 2031; i++)
{
DropDownList1.Items.Add(new ListItem(c(i)));
}
for (int i = 1; i < 13; i++)
{
DropDownList2.Items.Add(new ListItem(c(i)));
}
for (int i = 1; i < 32; i++)
{
DropDownList3.Items.Add(new ListItem(c(i)));
}
}
}
protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
DropDownList3.Items.Clear();
int days = DateTime.DaysInMonth(int.Parse(DropDownList1.SelectedValue), int.Parse(DropDownList2.SelectedValue));
for (int i = 1; i <= days; i++)
{
DropDownList3.Items.Add(new ListItem(c(i)));
}
}
string c(int i)
{
string u = i.ToString();
if (u.Length == 1) { u = "0" + u; }
return u;
}
}
