再谈 N 个 ASP.net DropDownList 无刷新联动菜单，牺牲N-1个ASPX来实现自动更新机制，避免刷新的闪动！！
以下代码绝对可以使用，也可以实现多级菜单。。。。
1<script language="javascript">
2function load(state)
3{
4var drp2 = document.getElementById("DropDownList2");
5for(var i=0;i<=drp2.options.length-1;i++)
6{
7drp2.remove(i);
8}
9var oHttpReq = new ActiveXObject("MSXML2.XMLHTTP"); //发送请求
10var oDoc = new ActiveXObject("MSXML2.DOMDocument"); //响应结果
11var state=document.getElementById("DropDownList1").value;
12oHttpReq.open("post","webform2.aspx?state="+state, false);
13oHttpReq.send("");
14result = oHttpReq.responseText;
15oDoc.loadXML(result);
16
17// items = oDoc.selectNodes("//CITY/Table");
18items = oDoc.selectNodes("//address/Table");
19for (var item = items.nextNode();item;item = items.nextNode())
20{
21var city = item.selectSingleNode("//address").nodeTypedValue;
22var newOption = document.createElement("OPTION");
23newOption.text = city;
24newOption.value = city;
25drp2.options.add(newOption);
26}
27}
28</script>
============================
webform1.aspx
private void Page_Load(object sender, System.EventArgs e)
{
// 在此处放置用户代码以初始化页面
if(!IsPostBack)
{
SqlConnection con = new SqlConnection("packet size=4096;user id=sa;data source=SERVER;persist security info=False;initial catalog=pubs");
SqlDataAdapter da = new SqlDataAdapter("select state from authors group by state",con);
DataSet ds = new DataSet("State");
da.Fill(ds);
this.DropDownList1.DataSource = ds.Tables[0];
this.DropDownList1.DataTextField = "state";
this.DropDownList1.DataValueField = "state";
this.DropDownList1.DataBind();
this.DropDownList1.Attributes.Add("onchange","load()");
//DropDownList1.
}
}
webform2.aspx
private void Page_Load(object sender, System.EventArgs e)
{
// 在此处放置用户代码以初始化页面
if(this.Request["state"]!=null)
{
string state = this.Request["state"].ToString();
SqlConnection con = new SqlConnection("packet size=4096;user id=sa;data source=SERVER;persist security info=False;initial catalog=pubs");
SqlDataAdapter da = new SqlDataAdapter("select address from authors where state = '"+state+"'",con);
DataSet ds = new DataSet("address");
da.Fill(ds);
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();
}
}