
1.html代码

<HTML>
<HEAD>
<title>XmlHttp实现无刷新三联动下拉框</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">
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="Form1" method="post" runat="server">
<INPUT style="Z-INDEX: 102; LEFT: 448px; WIDTH: 56px; POSITION: absolute; TOP: 80px; HEIGHT: 24px"
onclick="getData();" type="button" value="保存" id="Button1" name="Button1" runat="server">
<asp:TextBox id="TextBox1" style="Z-INDEX: 101; LEFT: 16px; POSITION: absolute; TOP: 80px" runat="server"
Width="424px"></asp:TextBox>
<asp:DropDownList id="DropDownList2" runat="server" style="Z-INDEX: 103; LEFT: 176px; POSITION: absolute; TOP: 120px"></asp:DropDownList>
<asp:DropDownList id="DropDownList1" runat="server" style="Z-INDEX: 104; LEFT: 16px; POSITION: absolute; TOP: 120px"></asp:DropDownList>
<asp:DropDownList id="DropDownList3" runat="server" style="Z-INDEX: 105; LEFT: 296px; POSITION: absolute; TOP: 120px"></asp:DropDownList><INPUT style="Z-INDEX: 106; LEFT: 8px; WIDTH: 160px; POSITION: absolute; TOP: 176px; HEIGHT: 22px"
type="hidden" size="21" id="hidprovince" runat="server"><INPUT style="Z-INDEX: 107; LEFT: 184px; POSITION: absolute; TOP: 176px" type="hidden"
id="hidcity" runat="server"><INPUT style="Z-INDEX: 108; LEFT: 360px; POSITION: absolute; TOP: 176px" type="hidden"
id="hidarea" runat="server">

<SCRIPT LANGUAGE="JavaScript">
<!--
//以XML求取DropDownList2的数据
function XmlPost2(obj)

{
var svalue = obj.value;
var webFileUrl = "?povinceid=" + svalue;
var result = "";
var xmlHttp = new ActiveXObject("MSXML2.XMLHTTP");
xmlHttp.open("POST", webFileUrl, false);
xmlHttp.send("");
result = xmlHttp.responseText;
if(result != "")

{
document.all("DropDownList2").length=0;
var piArray = result.split(",");
for(var i=0;i<piArray.length;i++)

{
var ary1 = piArray[i].toString().split("|");
document.all("DropDownList2").options.add(new Option(ary1[1].toString(),ary1[0].toString()));
}
}
else

{
alert(result);
}
}
//以XML求取DropDownList3的数据
function XmlPost3(obj)

{
var svalue = obj.value;
var webFileUrl = "?cityid=" + svalue;
var result = "";
var xmlHttp = new ActiveXObject("MSXML2.XMLHTTP");
xmlHttp.open("POST", webFileUrl, false);
xmlHttp.send("");
result = xmlHttp.responseText;
if(result != "")

{
document.all("DropDownList3").length=0;
var piArray = result.split(",");
for(var i=0;i<piArray.length;i++)

{
var ary1 = piArray[i].toString().split("|");
document.all("DropDownList3").options.add(new Option(ary1[1].toString(),ary1[0].toString()));
}
}
else

{
alert(result);
}
}
function getData()

{
var province=document.getElementById("DropDownList1");
var pindex = province.selectedIndex;
var pValue = province.options[pindex].value;
var pText = province.options[pindex].text;
var city=document.getElementById("DropDownList2");
var cindex = city.selectedIndex;
var cValue = city.options[cindex].value;
var cText = city.options[cindex].text;
var area=document.getElementById("DropDownList3");
var aindex = area.selectedIndex;
var aValue = area.options[aindex].value;
var aText = area.options[aindex].text;
var txt=document.getElementById("TextBox1");

document.getElementById("<%=TextBox1.ClientID%>").innerText="省:"+pValue+"|"+pText+"市:"+cValue+"|"+cText+"区:"+aValue+"|"+aText;
document.Form1.hidprovince.value=pValue;
document.Form1.hidcity.value=cValue;
document.Form1.hidarea.value=aValue;
}
//-->
</SCRIPT>
</form>
</body>
</HTML>
2.cs代码
public class WebForm1 : System.Web.UI.Page

{
protected System.Web.UI.WebControls.DropDownList DropDownList1;
protected System.Web.UI.WebControls.DropDownList DropDownList2;
protected System.Web.UI.WebControls.DropDownList DropDownList3;
protected System.Web.UI.WebControls.TextBox TextBox1;
public static string ConnectionString=System.Configuration .ConfigurationSettings .AppSettings["ConnectionString"];

GetDataSet#region GetDataSet
public static DataSet GetDataSet(string sql)

{
SqlDataAdapter sda =new SqlDataAdapter(sql,ConnectionString);
DataSet ds=new DataSet();
sda.Fill(ds);
return ds;
}
#endregion


property#region property
private string provinceid

{
get

{
if(ViewState["provinceid"]!=null && ViewState["provinceid"].ToString()!="")

{
return ViewState["provinceid"].ToString();
}
else

{
if(Request["provinceid"]!=null && Request["provinceid"].ToString()!="")

{
return Request["provinceid"];
}
else

{
return "";
}
}
}
set

{
ViewState["provinceid"]=value;
}
}
private string cityid

{
get

{
if(ViewState["cityid"]!=null && ViewState["cityid"].ToString()!="")

{
return ViewState["cityid"].ToString();
}
else

{
if(Request["cityid"]!=null && Request["cityid"].ToString()!="")

{
return Request["cityid"];
}
else

{
return "";
}
}
}
set

{
ViewState["cityid"]=value;
}
}
#endregion


Page_Load#region Page_Load
private void Page_Load(object sender, System.EventArgs e)

{
if(!this.IsPostBack)

{
this.down1_bind();
this.DropDownList1.Attributes.Add("onchange","XmlPost2(this);");
this.DropDownList2.Attributes.Add("onchange","XmlPost3(this);");
}
if(provinceid != "")

{
this.down2_bind(provinceid);
}
if(cityid != "")

{
this.down3_bind(cityid);
}
}
#endregion


down2_bind#region down2_bind
private void down2_bind(string id)

{
string mystr = "";
string sql = "select cityID,city from city where father = '" + id + "'";
DataSet ds = GetDataSet(sql);

if(ds.Tables[0].Rows.Count != 0)

{
for(int i=0;i<ds.Tables[0].Rows.Count;i++)

{
mystr += "," + ds.Tables[0].Rows[i][0].ToString() + "|" + ds.Tables[0].Rows[i][1].ToString();
}
mystr = mystr.Substring(1);
}
this.Response.Write(mystr);
this.Response.End();
}
#endregion


down3_bind#region down3_bind
private void down3_bind(string id)

{
string mystr = "";
string sql = "select areaID,area from area where father = '" + id + "'";
DataSet ds = GetDataSet(sql);

if(ds.Tables[0].Rows.Count != 0)

{
for(int i=0;i<ds.Tables[0].Rows.Count;i++)

{
mystr += "," + ds.Tables[0].Rows[i][0].ToString() + "|" + ds.Tables[0].Rows[i][1].ToString();
}
mystr = mystr.Substring(1);
}
this.Response.Write(mystr);
this.Response.End();
}

#endregion

down1_bind#region down1_bind
private void down1_bind()

{
string sql = "select provinceID,province from province";
DataSet ds = GetDataSet(sql);
this.DropDownList1.DataSource = ds;
this.DropDownList1.DataValueField = "provinceID";
this.DropDownList1.DataTextField = "province";
this.DropDownList1.DataBind();
}

#endregion


Web Form Designer generated code#region Web Form Designer generated code
override protected void OnInit(EventArgs e)

{
//
// CODEGEN: This call is required by the ASP.NET Web Form Designer.
//
InitializeComponent();
base.OnInit(e);
}


/**//// <summary>
/// Required method for Designer support - do not modify
/// the contents of this method with the code editor.
/// </summary>
private void InitializeComponent()

{
this.Load += new System.EventHandler(this.Page_Load);

}
#endregion
}
3.数据库area1.rar
4.Ajax实现无刷新三联动下拉框
5.源代码下载XmlHttpselect.rar