UpdatePanel控件实现无刷新级联

来源：互联网发布：循环遍历json对象编辑：程序博客网时间：2024/05/18 03:39

.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：

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