WebForm2.aspx,页面的代码如下:
<%@ Page language="c#" Codebehind="WebForm2.aspx.cs" AutoEventWireup="false" Inherits="WebApplication1.WebForm2" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm2</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
<script>
function load(id){
var drp2 = document.getElementById("DropDownList2");
for(var i = 0;i<=drp2.options.length -1;i++)
{
drp2.remove(i);
}
var oHttpReq = new ActiveXObject("MSXML2.XMLHTTP");
var oDoc = new ActiveXObject("MSXML2.DOMDocument");
oHttpReq.open("POST", "webform3.aspx?id="+id, false);
oHttpReq.send("");
result = oHttpReq.responseText;
oDoc.loadXML(result);
items = oDoc.selectNodes("//title/classa");
for (var item = items.nextNode(); item; item = items.nextNode())
{
var city = item.selectSingleNode("//title").nodeTypedValue;
var newOption = document.createElement("OPTION");
newOption.text = title;
newOption.value = classa;
drp2.options.add(newOption);
}
}
</script>
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<asp:DropDownList id="DropDownList1" style="Z-INDEX: 101; LEFT: 24px; POSITION: absolute; TOP: 32px"
runat="server"></asp:DropDownList>
<asp:DropDownList id="DropDownList2" style="Z-INDEX: 102; LEFT: 120px; POSITION: absolute; TOP: 32px"
runat="server"></asp:DropDownList>
</form>
</body>
</HTML>
上面的页面中有两个DropDownList和一段js脚本,下面是Page_Load里面的代码:if(!IsPostBack)
{
sqlConnection1.Open();
ds1=sqlCommand1.ExecuteReader();
DropDownList1.DataSource=ds1;
DropDownList1.DataTextField = "title";
DropDownList1.DataValueField = "id";
DropDownList1.DataBind();
ds1.Close();
sqlConnection1.Close();
DropDownList1.Attributes.Add("onchange","load(this.options[this.selectedIndex].innerText)");
}
下面WebFowm3.aspx内容Page_Load
if(this.Request["id"]!=null)
{
string id = this.Request["id"].ToString();
SqlConnection con = new SqlConnection("server=localhost;database=Northwind;uid=zhangbin;pwd=zb9119;");
SqlDataAdapter da = new SqlDataAdapter("select title,classa from classb where classa = '"+id+"'",con);
DataSet ds = new DataSet();
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(); }
<%@ Page language="c#" Codebehind="WebForm2.aspx.cs" AutoEventWireup="false" Inherits="WebApplication1.WebForm2" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>WebForm2</title>
<meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1">
<meta name="CODE_LANGUAGE" Content="C#">
<meta name="vs_defaultClientScript" content="JavaScript">
<meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5">
<script>
function load(id){
var drp2 = document.getElementById("DropDownList2");
for(var i = 0;i<=drp2.options.length -1;i++)
{
drp2.remove(i);
}
var oHttpReq = new ActiveXObject("MSXML2.XMLHTTP");
var oDoc = new ActiveXObject("MSXML2.DOMDocument");
oHttpReq.open("POST", "webform3.aspx?id="+id, false);
oHttpReq.send("");
result = oHttpReq.responseText;
oDoc.loadXML(result);
items = oDoc.selectNodes("//title/classa");
for (var item = items.nextNode(); item; item = items.nextNode())
{
var city = item.selectSingleNode("//title").nodeTypedValue;
var newOption = document.createElement("OPTION");
newOption.text = title;
newOption.value = classa;
drp2.options.add(newOption);
}
}
</script>
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<asp:DropDownList id="DropDownList1" style="Z-INDEX: 101; LEFT: 24px; POSITION: absolute; TOP: 32px"
runat="server"></asp:DropDownList>
<asp:DropDownList id="DropDownList2" style="Z-INDEX: 102; LEFT: 120px; POSITION: absolute; TOP: 32px"
runat="server"></asp:DropDownList>
</form>
</body>
</HTML>
上面的页面中有两个DropDownList和一段js脚本,下面是Page_Load里面的代码:if(!IsPostBack)
{
sqlConnection1.Open();
ds1=sqlCommand1.ExecuteReader();
DropDownList1.DataSource=ds1;
DropDownList1.DataTextField = "title";
DropDownList1.DataValueField = "id";
DropDownList1.DataBind();
ds1.Close();
sqlConnection1.Close();
DropDownList1.Attributes.Add("onchange","load(this.options[this.selectedIndex].innerText)");
}
下面WebFowm3.aspx内容Page_Load
if(this.Request["id"]!=null)
{
string id = this.Request["id"].ToString();
SqlConnection con = new SqlConnection("server=localhost;database=Northwind;uid=zhangbin;pwd=zb9119;");
SqlDataAdapter da = new SqlDataAdapter("select title,classa from classb where classa = '"+id+"'",con);
DataSet ds = new DataSet();
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(); }
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http://www.codeproject.com/aspnet/ScriptCallbackFramework.asp
ftp://uncj.net:[email protected]
。NET类\开发用的资源\DROPDOWN的三级例子.rar
http://www.codeproject.com/aspnet/ScriptCallbackFramework.asp
下面我将描述一种原始的方法,之所以说它原是是因为这种方法在ASP.NET之前就已经有了,我想这两者之间的关系我不必详细描述,我们今天要说的是如何不刷新页面更新DropDownList,该方法旨在抛砖引玉,其实使用该方法可以实现许多不刷新网页就和后台交互的应用,好了废话就不说了,看看我们的例子吧,首先我们需要一个放置两个DropDownList的页面,假如它叫WebForm2.aspx,页面的代码如下:
<%@ Page language="c#" Codebehind="WebForm2.aspx.cs" AutoEventWireup="false" Inherits="WebApptest1.WebForm2" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<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");
for(var i = 0;i<=drp2.options.length -1;i++){
drp2.remove(i);
}
var oHttpReq = new ActiveXObject("MSXML2.XMLHTTP");
var oDoc = new ActiveXObject("MSXML2.DOMDocument");
oHttpReq.open("POST", "webform6.aspx?state="+state, false);
oHttpReq.send("");
result = oHttpReq.responseText;
oDoc.loadXML(result);
items = oDoc.selectNodes("//CITY/Table");
for (var item = items.nextNode(); item; item = items.nextNode()){
var city = item.selectSingleNode("//city").nodeTypedValue;
var newOption = document.createElement("OPTION");
newOption.text = city;
newOption.value = city;
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> 上面的页面中有两个DropDownList和一段js脚本,该脚本可以直接写在页面也可以写在后台在Regeist到页面上(后者更灵活一些)该页的后台代码如下所示,在Page_Load里面写如下的代码:
if(!this.IsPostBack){
SqlConnection con = new SqlConnection("server=localhost;database=pubs;uid=sa;pwd=sa;");
SqlDataAdapter da = new SqlDataAdapter("select state from authors group by state",con);
DataSet ds = new DataSet();
this.DropDownList1.DataTextField = "State";
this.DropDownList1.DataValueField = "State";
this.DropDownList1.DataBind();
this.DropDownList1.Attributes.Add("onchange","load(this.options[this.selectedIndex].innerText)");
}
在上面的代码中我们做了两件事情:1、帮定其中一个DropDownList(你也可以同时绑定两个)。2、指定该控件的客户端脚本。下面我们详细介绍一下上面的js代码,首先得到页面上要联动的DorpDownList对象,将他的Options清空,再创建两个客户端对象oHttpReq和oDoc对象,其中一个负责发送请求另一个负责得到响应结果,我们将用户选择的State发送到名为WebForm6.aspx的页面,该页面将处理这个请求并返回一个响应,该响应的结果是一个XML文件,稍候介绍WebForm6.aspx里面的代码。我们将返回的结果使用loadXML方法Load到oDoc对象里面,然后就可以使用selectNodes方法得到所有的city节点,接着循环这些节点在客户端创建Option对象,最后将这些Option对象Add到DropDwonList2里面去。
下面我们看看WebFowm6.aspx都做了些什么事情,该页面的HTML页面是一个除了包括<@Page>指令意外什么都没有的页面,后台的Page_Load代码如下:
private void Page_Load(object sender, System.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=localhost;database=pubs;uid=sa;pwd=sa;");
SqlDataAdapter da = new SqlDataAdapter("select city from authors where state = '"+state+"'",con);
DataSet ds = new DataSet("CITY");
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();
}
该方法得到用户选择的state通过查询以后得到一个DataSet对象,使用该对象的WriteXML方法直接将内容写到Response.OutputStream里面然后传递到客户端,客户端的load方法通过result =oHttpReq.responseText;句话得到一个XML字符串,最后解析此串。