使用 AjaxPro 来完成二级联动的效果

现在在实现二级连动或是三级连动方面，都是采用ajax来完成的。网上的例子也很多。 我采用的是AjaxPro来完的。 如何配置AjaxPro我就不说了。
BigClassid 前台页面

＜script type="text/javascript"＞
function ShowCity(id)
{
var result = chen.getCityList(id).value;
var ddlcity = document.getElementById("ddlCity");
ddlcity.length=0;
for(var i=0; i＜result.Rows.length; i++)
{
ddlcity.options.add(new Option(result.Rows[i].SmallClass,result.Rows[i].id));
}
}
＜/script＞
＜/head＞
＜body＞
＜form id="form1" runat="server"＞
＜p＞
省份：＜asp:DropDownList ID="ddlPro" runat="server"＞
＜/asp:DropDownList＞
市区：＜asp:DropDownList ID="ddlCity" runat="server"＞
＜/asp:DropDownList＞
＜/p＞
＜div＞

＜/div＞
＜/form＞
＜/body＞
＜script type="text/javascript"＞
function ShowCity(id)
{
var result = chen.getCityList(id).value;
var ddlcity = document.getElementById("ddlCity");
ddlcity.length=0;
for(var i=0; i＜result.Rows.length; i++)
{
ddlcity.options.add(new Option(result.Rows[i].SmallClass,result.Rows[i].id));
}
}
＜/script＞
＜/head＞
＜body＞
＜form id="form1" runat="server"＞
＜p＞
省份：＜asp:DropDownList ID="ddlPro" runat="server"＞
＜/asp:DropDownList＞
市区：＜asp:DropDownList ID="ddlCity" runat="server"＞
＜/asp:DropDownList＞
＜/p＞
＜div＞

＜/div＞
＜/form＞
＜/body＞

后台：


[AjaxPro.AjaxNamespace("chen")]


public partial class ddlTwo : System.Web.UI.Page


{


protected void Page_Load(object sender, EventArgs e)


{


AjaxPro.Utility.RegisterTypeForAjax(typeof(ddlTwo));




SqlConnection conn = new SqlConnection("server=.; uid=sa; pwd=chen123; database=C_News; ");


conn.Open();


SqlCommand cmd = new SqlCommand("", conn);


string strsql = "select * from C_BigClass";


cmd.CommandText = strsql;


SqlDataAdapter da = new SqlDataAdapter();


da.SelectCommand = cmd;


DataTable dt = new DataTable();


da.Fill(dt);




this.ddlPro.DataSource = dt;


this.ddlPro.DataValueField = "id";


this.ddlPro.DataTextField = "BigClass";


this.ddlPro.DataBind();




this.ddlPro.Attributes["onchange"] = "ShowCity(this.options[selectedIndex].value)";




conn.Close();


}




[AjaxPro.AjaxMethod]


public DataTable getCityList(int id)


{


Hashtable ht = new Hashtable();




SqlConnection conn = new SqlConnection("server=.; uid=sa; pwd=chen123; database=C_News; ");


conn.Open();


SqlCommand cmd = new SqlCommand("", conn);


string strsql = "select * from C_SmallClass where BigClassid="+id+"";


cmd.CommandText = strsql;


SqlDataAdapter da = new SqlDataAdapter();


da.SelectCommand = cmd;


DataTable dt = new DataTable();


da.Fill(dt);




return dt;


}


}

　　如果我们要进行三级或四级连动，其实很简单，只要在Page_load下面this.ddlPro.Attributes["onchange"] = "ShowCity(this.options[selectedIndex].value)"; 的下面为每个下拉框都加一个方法就行了。只不过多写几个public DataTable getCityList(int id)的程序。

.pb{}
.pb textarea{font-size:14px; margin:10px; font-family:"宋体"; background:#FFFFEE; color:#000066}
.pb_t{line-height:30px; font-size:14px; color:#000; text-align:center;}
/* 分页 */
.pagebox{overflow:hidden; zoom:1; font-size:12px; font-family:"宋体",sans-serif;}
.pagebox span{float:left; margin-right:2px; overflow:hidden; text-align:center; background:#fff;}
.pagebox span a{display:block; overflow:hidden; zoom:1; _float:left;}
.pagebox span.pagebox_pre_nolink{border:1px #ddd solid; width:53px; height:21px; *height:23px; line-height:21px; text-align:center; color:#999; cursor:default;}
.pagebox span.pagebox_pre{color:#3568b9; height:23px;}
.pagebox span.pagebox_pre a,.pagebox span.pagebox_pre a:visited,.pagebox span.pagebox_next a,.pagebox span.pagebox_next a:visited{border:1px #9aafe5 solid; color:#3568b9; text-decoration:none; text-align:center; width:53px; cursor:pointer; height:21px; *height:23px; line-height:21px;}
.pagebox span.pagebox_pre a:hover,.pagebox span.pagebox_pre a:active,.pagebox span.pagebox_next a:hover,.pagebox span.pagebox_next a:active{color:#363636; border:1px #2e6ab1 solid;}
.pagebox span.pagebox_num_nonce{padding:0 8px; height:23px; line-height:23px; color:#fff; cursor:default; background:#296cb3; font-weight:bold;}
.pagebox span.pagebox_num{color:#3568b9; height:23px;}
.pagebox span.pagebox_num a,.pagebox span.pagebox_num a:visited{border:1px #9aafe5 solid; color:#3568b9; text-decoration:none; padding:0 8px; cursor:pointer; height:21px; *height:23px; line-height:21px;}
.pagebox span.pagebox_num a:hover,.pagebox span.pagebox_num a:active{border:1px #2e6ab1 solid;color:#363636;}
.pagebox span.pagebox_num_ellipsis{color:#393733; width:22px; background:none; line-height:23px;}
.pagebox span.pagebox_next_nolink{border:1px #ddd solid; width:53px; height:21px; *height:23px; line-height:21px; text-align:center; color:#999; cursor:default;}