script不刷新页面的联动前后代码

<asp:DropDownList ID="type1" runat="server" CssClass="tfont" onchange="link(this.id);" </asp:DropDownList> 
<%-- 大小类--%> 
<script> 
function link(id) 
{ 
var obj = document.getElementById(id); 
var obj1 = document.getElementById('type2'); 
var name = ""; 
for(i = 0 ; i < obj.options.length ; i++ ) 
{ 
if(obj.options[i].selected) 
{ 
name = obj.options[i].value; 
} 
} 
var names = bargain_class.link(name).value.split(','); 
var obj1_count = obj1.options.length 
for (i = 0 ; i < obj1_count ; i++) 
{ 
obj1.options.remove(0); 
} 
for (i = 0 ; i < names.length ; i ++ ) 
{ 
option1 = document.createElement("option"); 
option1.innerHTML = names[i]; 
obj1.appendChild(option1); 
} 
// alert(names); 
} 
</script> //后台代码 
AjaxPro.Utility.RegisterTypeForAjax(typeof(bargain_class)); //本页页面名 
//===============================ajax调用===================================== 
[AjaxPro.AjaxMethod] 
public string link(string name) 
{ 
string text = ""; 
string sql = "select name from Management_products_class where pid='" + name + "'"; 
DataTable dt = LinkSql.conn(sql); 
for (int i = 0; i < dt.Rows.Count; i++) 
{ 
if (text == "") 
{ 
text = dt.Rows[i]["name"].ToString(); 
} 
else 
{ 
text += "," + dt.Rows[i]["name"].ToString(); 
} 
} 
return text; 
}