asp.net实现DropDownList、ListBox无刷新三级联动(javascript)

此为DropDownList无刷新三级联动的另一种方法，使用javascript操作，因是在客户端操作，所以切换速度较快，但如果数据量大时，加载时会稍慢点，下一篇文章我会发布针对此方法的改进方案，供大家参考。此为DropDownList示例，ListBox只需略加修改。

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数据库下载
/Files/netshuai/area.rar

aspx页面代码

   
<% =strAreaData %>
 <script language = "JavaScript" type="text/javascript">

    function changearea1()
    {
    document.all("<% =Ddl_AreaTwo.ClientID %>").length = 0; 
    document.all("<% =Ddl_AreaTwo.ClientID %>").options[0] = new Option('选择城市','0');
    document.all("<% =Ddl_AreaThree.ClientID %>").length = 0; 
    document.all("<% =Ddl_AreaThree.ClientID %>").options[0] = new Option('选择城市','0');
    var oneid=document.all("<% =Ddl_AreaOne.ClientID %>").value;
    var i;
    for (i=0;i < onecount; i++)
        {
            if (subcat[i][1] == oneid)
            { 
                document.all("<% =Ddl_AreaTwo.ClientID %>").options[document.all("<% =Ddl_AreaTwo.ClientID %>").length] = new Option(subcat[i][0], subcat[i][2]);
            }        
        }
        
    }
    
        function changearea2()
    {
    document.all("<% =Ddl_AreaThree.ClientID %>").length = 0; 
    document.all("<% =Ddl_AreaThree.ClientID %>").options[0] = new Option('选择城市','0');
    var twoid=document.all("<% =Ddl_AreaTwo.ClientID %>").value;
    var oneid=document.all("<% =Ddl_AreaOne.ClientID %>").value;
    var i;
    for (i=0;i < onecount1; i++)
        {
            if (subcat1[i][2] == twoid)
            { 
                if (subcat1[i][1] == oneid)
                {
                    document.all("<% =Ddl_AreaThree.ClientID %>").options[document.all("<% =Ddl_AreaThree.ClientID %>").length] = new Option(subcat1[i][0], subcat1[i][3]);
                }        
            }
        }
    }      
    
    </script>                
                    <asp:DropDownList ID="Ddl_AreaOne" runat="server"  AppendDataBoundItems="True">
                        <asp:ListItem Value="0">请选择</asp:ListItem>
                    </asp:DropDownList>
                    <asp:DropDownList ID="Ddl_AreaTwo" runat="server" >
                        <asp:ListItem Value="0">请选择</asp:ListItem>
                    </asp:DropDownList>
                    <asp:DropDownList ID="Ddl_AreaThree" runat="server" >
                        <asp:ListItem Value="0">请选择</asp:ListItem>
                    </asp:DropDownList>

cs页面代码

protected string strAreaData;
    protected void Page_Load(object sender, EventArgs e)
    {
        Ddl_AreaOne.Attributes.Add("onchange", "changearea1()");
        Ddl_AreaTwo.Attributes.Add("onchange", "changearea2()");
        string strSQL;
        strSQL = "select * from nts_area where oneid<>0 and twoid=0 and threeid=0 order by sort";
        Ddl_AreaOne.DataSource = DataClass.GetDataReader(strSQL);
        Ddl_AreaOne.DataTextField = "areaname";
        Ddl_AreaOne.DataValueField = "oneid";
        Ddl_AreaOne.DataBind();
        strAreaData = "<script language = 'JavaScript' type='text/javascript'>var onecount;onecount=0;subcat = new Array();";
        strSQL = "select * from nts_area where oneid<>0 and twoid<>0 and threeid=0 order by sort";
        string ConnectionString="Provider=Microsoft.Jet.OLEDB.4.0;Data Source='数据库路径'";
        OleDbConnection cnn = new OleDbConnection(ConnectionString);
        cnn.Open();
        OleDbCommand cmd=new OleDbCommand(sql, cnn);
        OleDbDataReader dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        int i1 = 0;
        while (dr.Read())
        {
            strAreaData += "subcat[" + i1.ToString() + "] = new Array('" + dr["areaname"].ToString() + "','" + dr["oneid"].ToString() + "','" + dr["twoid"].ToString() + "');";
            i1++;

        }
        strAreaData += "onecount=" + i1.ToString() + ";";

        //添加三级地区
        strAreaData += "var onecount1;onecount1=0;subcat1 = new Array();";

        strSQL = "select * from nts_area where oneid<>0 and twoid<>0 and threeid<>0 order by sort";
        cnn.Open();
        cmd.CommandText = strSQL;
        cmd.Connection = cnn;
        dr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
        int n1 = 0;
        while (dr.Read())
        {
            strAreaData += "subcat1[" + n1.ToString() + "] = new Array('" + dr["areaname"].ToString() + "','" + dr["oneid"].ToString() + "','" + dr["twoid"].ToString() + "','" + dr["threeid"].ToString() + "');"; n1++;

        }
        dr.Close();
        strAreaData += "onecount1=" + n1.ToString() + ";</script>";
    }