基于jquery ajax实现DropDownList二级联动

using System.Web.Services;
// 实现下拉框二级联动AJAX请求加载数据方法
    [WebMethod()]
    public static ArrayList GetSubList(string sBuyID)
    {
        ArrayList subList = new ArrayList();

        if (sBuyID == "1")
        {
            subList.Add(new ListItem("文艺", "1"));
            subList.Add(new ListItem("少儿", "2"));
            subList.Add(new ListItem("人文社科", "3"));
            subList.Add(new ListItem("科技", "4"));
        }
        else if (sBuyID == "2")
        {
            subList.Add(new ListItem("手机通讯", "1"));
            subList.Add(new ListItem("手机配件", "2"));
            subList.Add(new ListItem("摄影摄像", "3"));
            subList.Add(new ListItem("数码配件", "4"));
        }

        return subList;
    }