通过后台文件（cs）向页面注册脚本

 protected void Page_Load(object sender, EventArgs e)
    {
        if(!IsPostBack)
        {
            string ScriptStirng = "<script type='text/javascript' >alert('弹出');</script>";
            if (!IsClientScriptBlockRegistered("CSscript"))
            {
                RegisterClientScriptBlock("CSscript", ScriptStirng); 
            }
               
        }
      
    }