以xml数据源作无限级联动下拉框

var MenuInfo = Class.create();
MenuInfo.prototype = {
initialize : function(sParentValue, sValue, sDesc) {
this.parentValue = sParentValue;
this.Value = sValue;
this.Desc = sDesc;
}
}

function V(ele, attr) {
return ele.getAttribute(attr);
}

function createXMLDom() {
if (window.ActiveXObject)
var xmldoc = new ActiveXObject(“Microsoft.XMLDOM”);
else
if (document.implementation&&document.implementation.createDocument)
var xmldoc = document.implementation.createDocument(“”,”doc”,null);
xmldoc.async = false;
xmldoc.preserveWhiteSpace=true;
return xmldoc;
}

function loadXML(dataSrc, xmlFile) {
if (xmlFile == null) {
if (window.ActiveXObject) {
return (dataSrc).documentElement;
} else {
for (i=0; i<(dataSrc).childNodes.length; i++) {
if ((dataSrc).childNodes[i].tagName != null) {
return (dataSrc).childNodes[i];
break;
}
}
}
} else {
var xmlDom = createXMLDom();
try{
xmlDom.load(xmlFile);
}catch(e){
alert(“lost xml File”);
}
return xmlDom.documentElement;
}
}
2.简单的控件类 必须的属性有USEDATA和Xml,USEDATA可以随便指定,应该是为了页面上有多个联动而设计的,现在没有支持,另一个xml属性用于指定xml格式数据源 ,另外依赖于外部js /Script/linkage.js和/Script/prototype.js
.using System;
using System.Collections.Generic;
using System.Text;
using System.Xml;
using System.Web.UI.WebControls;
using System.Web.UI;
using System.ComponentModel;
using System.Collections.Specialized;

namespace Blackant.Controls
{
[DefaultProperty("Value")]
public class AssociatedDropDownList : WebControl, IPostBackDataHandler
{

字段#region 字段
private string _Xml=”<root/>”;
private XmlDocument _XmlDoc;

#endregion
属性#region 属性
[Bindable(true)]
[Category("Appearance")]
[DefaultValue("0")]
[Localizable(true)]
public string Value
{
get
{
return ViewState["Value"] == null ? “0″ : ViewState["Value"].ToString();
}
set
{
ViewState["Value"] = value;

}
}

public string USEDATA
{
get
{
if (ViewState["USEDATA"] != null)
return ViewState["USEDATA"].ToString();
return String.Empty;
}
set { ViewState["USEDATA"] = value; }
}

/**//// <summary>
/// 字符串形式表达的xml格式文档
/// </summary>
public string Xml {
get { return _Xml; }
set { _Xml = value;

}
}
#endregion

私有方法#region 私有方法
int GetMaxLevel(XmlNode parent, int CurLevel)
{
int MaxLevel = CurLevel;
foreach (XmlNode xn in parent.ChildNodes)
{
if (xn.NodeType == XmlNodeType.Element)
{
int tmpLevel = GetMaxLevel(xn, CurLevel + 1);
MaxLevel = MaxLevel > tmpLevel ? MaxLevel : tmpLevel;
}
}
return MaxLevel;
}
#endregion
重载事件#region 重载事件

protected override void CreateChildControls()
{
_XmlDoc = new XmlDocument();
_XmlDoc.LoadXml(_Xml);

XmlElement root = _XmlDoc.DocumentElement;
int maxLevel = GetMaxLevel(root, 1);
for (int i = 1; i < maxLevel; i++)
{
DropDownList ddl = new DropDownList();
ddl.Attributes.Add(“USEDATA”, USEDATA);
ddl.Attributes.Add(“SUBCLASS”, i.ToString());
ddl.ID = ddl.ClientID;
Controls.Add(ddl);
}

base.CreateChildControls();
}

protected override void OnPreRender(EventArgs e)
{
Page.RegisterRequiresPostBack(this);
Page.ClientScript.RegisterHiddenField(this.ClientID, Value);
base.OnPreRender(e);
}
protected override void Render(HtmlTextWriter writer)
{

StringBuilder sb = new StringBuilder();
sb.AppendFormat(“<xml id=”{0}” style=”height:0px; width:0px; visibility:hidden;”>”, USEDATA);
sb.Append(_Xml);
sb.Append(“</xml>”);
sb.Append(” <script charset=”gb2312″ type=”text/javascript” src=”/Script/prototype.js”></script> “);
sb.Append(“<script charset=”gb2312″ type=”text/javascript” src=”/Script/linkage.js”></script> “);
sb.Append(“<script type=’text/javascript’>”);
sb.AppendFormat(“var linkage = new Linkage(“{0}”);”, USEDATA);
sb.Append(“linkage.init();”);
XmlNode xn = _XmlDoc.DocumentElement.SelectSingleNode(“//*[@Value=\'" + Value + "\']“);
List<string> init = new List<string>();
if (xn != null)
{

while (xn != _XmlDoc.DocumentElement)
{
init.Insert(0, xn.Attributes["Value"].Value);
xn = xn.ParentNode;
}
}
for (int i = 0; i < init.Count; i++)
{
sb.AppendFormat(“linkage.initLinkage(“{0}”,”{1}”,{2});”, USEDATA, init[i], i + 1);
}
sb.Append(“function SetAssociatedDropDownListValue(obj){var val=obj.value;while(val==”" && obj.previousSibling){obj=obj.previousSibling;val=obj.value;}(‘”+ClientID+”‘).value=val;}”);
sb.Append(“</script>”);

Page.ClientScript.RegisterStartupScript(typeof(string), USEDATA, sb.ToString());

base.Render(writer);
}
#endregion

IPostBackDataHandler Members#region IPostBackDataHandler Members

//private static readonly object EventTextChanged = new object();

public virtual bool LoadPostData(string postDataKey, NameValueCollection postCollection)
{
//比较初始数据presentValue和回传数据postedValue
string postedValue = postCollection[postDataKey];
string presentValue = Value;
if (presentValue == null || postedValue != presentValue)
{
Value = postedValue;
return true;
}
return false;
}
void IPostBackDataHandler.RaisePostDataChangedEvent()
{

}

#endregion
}
}
3简单运用,
<%@ Page Language=”C#” %>

<%@ Register Assembly=”Blackant.Controls” Namespace=”Blackant.Controls” TagPrefix=”bawc” %>

<!DOCTYPE html PUBLIC “-//W3C//DTD XHTML 1.0 Transitional//EN” “http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd”>

<script runat=”server”>

protected override void OnLoad(EventArgs e)
{

AssociatedDropDownList1.USEDATA = “test”;
AssociatedDropDownList1.Xml = @”
<TreeNodes>
<TreeNode Desc=”"湖北省”" Value=”"HB”">
<TreeNode Desc=”"荆门市”" Value=”"JM”"></TreeNode>
<TreeNode Desc=”"武汉市”" Value=”"WH”">
<TreeNode Desc=”"汉口”" Value=”"HK”"></TreeNode>
<TreeNode Desc=”"武昌”" Value=”"WC”"></TreeNode>
</TreeNode>
</TreeNode>
<TreeNode Desc=”"北京市”" Value=”"BJ”">
</TreeNode>
</TreeNodes>

“;

base.OnLoad(e);
}

protected void btnSubmit_Click(object sender, EventArgs e)
{
Response.Write(“当前选择:”+AssociatedDropDownList1.Value);
}
</script>