1.首先页面要继承ICallbackEventHandler

2.定义变量，用于传值protected string _callbackResult = "";

3.在 Page_Load里声明：

            string cbReference = Page.ClientScript.GetCallbackEventReference(this,"arg","getResultFromServer","context");
            string cbScript = "function useCallBack(arg,context){" + cbReference + "}";
            Page.ClientScript.RegisterClientScriptBlock(this.GetType(), "useCallBack", cbScript, true);

4.定义ICallbackEventHandler必须实现的两个方法：

        public void RaiseCallbackEvent(string str)
        {
            DataSet ds = prc.proBasicInfoSelect(str);

            if (ds.Tables[0].Rows.Count > 0)
            { _callbackResult = ds.Tables[0].Rows[0]["proManager"].ToString(); }
           
        }

        public string GetCallbackResult()
        {
            return _callbackResult;
        }

5.客户端处理：

客户端控件只需要调用useCallBack('','')方法即可，如果是按钮可用onclick="useCallBack('','');"调用

例外定义函数获得变量：

     function getResultFromServer(arg,context)
     {
      var lblPM = document.getElementById("lblPM");
      lblPM.innerText = arg;
     }