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所谓DropdownList联动，也就是在选一个DropdownList的时候使另外一个DropdownList的内容更新（如选省份时显示所属城市），按常规的方法那就是在第一个DropdownList的SelectedIndexChanged事件中改变第二个DropdownList的数据源及重新绑定，但是如果这样的话在每一次的重新选择将带来一次页面的刷新，除了屏幕闪动以外，如果同页有密码框的话，内容也会清除掉．这时我们就需要无刷新实现，基本原理在选择改变时用JS向另外一个隐藏页发送请求并得到一个XML流，解析后放入相应的DropdownList中．例子如下：
第一个页面：
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="jilian1.aspx.cs" Inherits="jilian1" %>
<!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>WebForm2</title>
<meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
<script>
function load(state) {
var drp2 = document.getElementById("DropDownList2");
var drpleng = drp2.options.length;
for (var i = drpleng - 1; i >=0; i--) {
drp2.remove(i);
}
//新建一请求与XML文档
var oHttpReq = new ActiveXObject("MSXML2.XMLHTTP");
var oDoc = new ActiveXObject("MSXML2.DOMDocument");
//将请求发送到另一页,其中参数state代表DropDownList1所选值
oHttpReq.open("POST", "jilian2.aspx?state=" + state, false);
oHttpReq.send("");
//取返回结果并放入XML文档中
result = oHttpReq.responseText;
oDoc.loadXML(result);
//设置根结点及循环读取其内容
items = oDoc.selectNodes("//Name/Table"); //CITY代表数据集名,Table代表数据集中的表名
for (var item = items.nextNode(); item; item = items.nextNode()) {
//var city = item.selectSingleNode("//city").nodeTypedValue; //city为所取字段内容
var city = item.nodeTypedValue;
var newOption = document.createElement("OPTION");
newOption.text = city; //下拉框的文本,如北京
newOption.value = city; //下拉框的值,如110000
drp2.options.add(newOption);
}
}
</script>
</head>
<body MS_POSITIONING="flowLayout">
<form id="Form1" method="post" runat="server">
<asp:DropDownList id="DropDownList1" runat="server"></asp:DropDownList>
<asp:DropDownList id="DropDownList2" runat="server"></asp:DropDownList>
</form>
</body>
</html>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
public partial class jilian1 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
if (!this.IsPostBack)
{
//string strsql = "select * from NodeType where [type]=‘Catalog‘ and DocTypeId=‘" + docTypeId + "‘ order by DocTypeId";
//DataTable dt = docSystemAccess.QueryDataTable(strsql);
SqlConnection con = new SqlConnection("server=127.0.0.1\\SQLDATA;uid=sa;pwd=bkin123;database=DocSystem");
SqlDataAdapter da = new SqlDataAdapter("select name,id from NodeType where [type]=‘Catalog‘ and DocTypeId=‘240a3d78-d8f1-4421-a170-9f5400e0e9ec‘ order by DocTypeId", con);
DataSet ds = new DataSet("name"); //此处CITY表示数据集名,与上面取数据时一致
da.Fill(ds);
this.DropDownList1.DataSource = ds;
this.DropDownList1.DataTextField = "name";
this.DropDownList1.DataValueField = "id";
this.DropDownList1.DataBind();
//添加一个属性,使其选择改变时调用上面的load方法,此处为文本,传值的话将innerText改为value即可.
this.DropDownList1.Attributes.Add("onchange", "load(this.options[this.selectedIndex].value)");
}
}
}
第二个页面：
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data.SqlClient;
using System.Data;
using System.Xml;
public partial class jilian2 : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
// Put user code to initialize the page here
if (this.Request["state"] != null)
{
string state = this.Request["state"].ToString();
SqlConnection con = new SqlConnection("server=127.0.0.1\\SQLDATA;uid=sa;pwd=bkin123;database=DocSystem");
SqlDataAdapter da = new SqlDataAdapter("select Name from NodeType where [type]=‘Catalog‘ and DocTypeId=‘240a3d78-d8f1-4421-a170-9f5400e0e9ec‘ and AllowAppendNodeType like ‘%" + state + "%‘ order by DocTypeId", con);
DataSet ds = new DataSet("Name"); //此处CITY表示数据集名,与上面取数据时一致
da.Fill(ds);
//string strsql = "select Name from NodeType where [type]=‘Catalog‘ and DocTypeId=‘240a3d78-d8f1-4421-a170-9f5400e0e9ec‘ and AllowAppendNodeType like ‘%" + state + "%‘ order by DocTypeId";
//DataTable dt = docSystemAccess.QueryDataTable(strsql);
//DataSet ds = new DataSet("Name");
//ds.Tables.Add(dt);
XmlTextWriter writer = new XmlTextWriter(Response.OutputStream, Response.ContentEncoding);
writer.Formatting = Formatting.Indented;
writer.Indentation = 4;
writer.IndentChar = ‘ ‘;
ds.WriteXml(writer);
writer.Flush();
Response.End();
writer.Close();
}
}
}
ASP_NET实现界面无刷新的DropdownList两级联动效果
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原文地址：http://www.cnblogs.com/hpbkin/p/4672818.html
