public partial class Base_WuLSearch : System.Web.UI.Page
{
     
    protected void Page_Load(object sender, EventArgs e)
    {
        Ajax.Utility.RegisterTypeForAjax(typeof(Base_WuLSearch));//注册类
  }
    [Ajax.AjaxMethod()] //说明函数是 ajax 方法
    public string getWLNum(string WuLNum)
    {
        return "chy";
}

<input type="button"  />

function callServer()
{
    Base_WuLSearch.getWLNum("100-1",CallBack); 调用后台的ajax 函数
}

function CallBack(response) //回掉函数 参数一定为  response 
{
  alert(response.value);  //----------显示 chy
}

<httpHandlers>
  <add verb="OST,GET" path="ajax/*.ashx" type="Ajax.PageHandlerFactory, Ajax"/>
  </httpHandlers>
  </system.web>