.master代码如下：
<%@ Master Language="VB" CodeFile="0_MST_ASPNET12.master.vb" Inherits="_0_MST_ASPNET12" %>
<!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>
<link href="CSS/CSS_DEFAULT.css" rel="stylesheet" type="text/css" />
<link href ="JS/jquery-1.9.1.js" type ="text/javascript" />
<asp:ContentPlaceHolder id="head" runat="server">
</asp:ContentPlaceHolder>
</head>
<body>
<form id="form1" runat="server">
<div style ="width:720px; margin:0px auto;">
<div id="div_nav">
<asp:Menu ID="Menu1" runat="server" DataSourceID="SiteMapDataSource1"
Orientation="Horizontal" StaticDisplayLevels="2">
</asp:Menu>
<asp:SiteMapDataSource ID="SiteMapDataSource1" runat="server" />
</div>
<%--说明性文字--%>
<div id="div_memo">
<asp:ContentPlaceHolder id="CPH_memo" runat="server" />
</div>
<%--主程序及控件--%>
<div id="div_main">
<asp:ContentPlaceHolder id="cph_main" runat="server"/>
</div>
<%--输出部分--%>
<div id="div_result">
<h4>输出检测内容:</h4>
<asp:ContentPlaceHolder id="cph_output" runat="server"/>
</div>
</div>
</form>
</body>
</html>
.aspx代码如下：
<%@ Page Title="" Language="C#" MasterPageFile="~/0_MST_ASPNET12.master" AutoEventWireup="true" CodeFile="S4_UpdatePanel_ddls.aspx.cs" Inherits="Sample_code_S4_UpdatePanel_ddls" %>
<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="CPH_memo" Runat="Server">
<strong>级联查询DropDownList:</strong>
<ul>
<li>ddl_p[省],内容不会改变,放在UpdatePanel外</li>
<li>设置Triggers -> ddl_p</li>
<li>ddl_c[市]数据绑定之后,会再次影响ddl_d的数据,所以绑定完成之后,需要强制ddl_d再次绑定数据</li>
<li>掌握数据绑定在页面生命周期中的位置</li>
</ul>
</asp:Content>
<asp:Content ID="Content3" ContentPlaceHolderID="cph_main" Runat="Server">
<p class ="showtime">页面时间: <%=DateTime.Now.ToFileTime() %></p>
请选择地区:
<asp:DropDownList ID="ddl_p" runat="server" DataSourceID="ads_p"
DataTextField="p_name" DataValueField="p_id" AutoPostBack="True">
</asp:DropDownList>
<asp:AccessDataSource ID="ads_p" runat="server" DataFile="~/DATA/China.mdb"
SelectCommand="SELECT * FROM [T_Province]"/>
<asp:ScriptManager ID="ScriptManager1" runat="server">
</asp:ScriptManager>
<asp:UpdatePanel ID="Upnl_ddls" runat="server" RenderMode="Inline"
UpdateMode="Conditional"> <%--RenderMode="Inline" 以流的方式显示（行显示）--%>
<ContentTemplate>
<asp:DropDownList ID="ddl_c" runat="server" DataSourceID="ads_c"
DataTextField="c_name" DataValueField="c_id" AutoPostBack="True" OnDataBound="load_d"><%--OnDataBound="load_d"强制绑定一下--%>
</asp:DropDownList>
<asp:AccessDataSource ID="ads_c" runat="server" DataFile="~/DATA/China.mdb"
SelectCommand="SELECT [c_name], [c_id] FROM [T_City] WHERE ([c_pid] = ?)">
<SelectParameters>
<asp:ControlParameter ControlID="ddl_p" Name="c_pid"
PropertyName="SelectedValue" Type="Int32" />
</SelectParameters>
</asp:AccessDataSource>
<asp:DropDownList ID="ddl_d" runat="server" DataSourceID="ads_d" OnDataBound="checkitems"
DataTextField="d_name" DataValueField="d_id">
</asp:DropDownList>
<asp:AccessDataSource ID="ads_d" runat="server" DataFile="~/DATA/China.mdb"
SelectCommand="SELECT [d_id], [d_name] FROM [T_District] WHERE ([d_cid] = ?)">
<SelectParameters>
<asp:ControlParameter ControlID="ddl_c" Name="d_cid"
PropertyName="SelectedValue" Type="Int32" />
</SelectParameters>
</asp:AccessDataSource>
<p class ="showtime">UpdatePanel时间: <%=DateTime.Now.ToFileTime() %></p>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID ="ddl_p" />
</Triggers>
</asp:UpdatePanel>
</asp:Content>
<asp:Content ID="Content4" ContentPlaceHolderID="cph_output" Runat="Server">
<asp:Button ID="Button1" runat="server" Text="读取选择" onclick="Button1_Click" />
<asp:Label ID="lbl_result" runat="server" />
</asp:Content>
注意点：
<span style="background-color: rgb(204, 0, 0);"> RenderMode="Inline" </span>
<span style="background-color: rgb(204, 0, 0);"> OnDataBound="load_d"</span>
.aspx.cs代码如下：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
public partial class Sample_code_S4_UpdatePanel_ddls : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
}
//第二个DDL,数据绑定完成后,要求第三个DDL重新进行数据绑定
protected void load_d(object sender, EventArgs e) {
ddl_d.DataBind();
}
//最后一个DDL,如果内容为空,则不显示
protected void checkitems(object s, EventArgs e) {
if (ddl_d.Items.Count == 0) { ddl_d.Style["display"] = "none"; } else { ddl_d.Style.Remove("display"); }
}
//读取选择的按钮
protected void Button1_Click(object sender, EventArgs e)
{
string _s = "您选择的是:" + ddl_p.SelectedItem.Text + " / " + ddl_c.SelectedItem.Text + " / " + ddl_d.SelectedItem.Text + "。";
lbl_result.Text = _s;
}
}
效果如下：
时间： 2024-07-30 01:48:43