asp.net 加页面Loading效果

        protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack)
            {
                Loading();
            }
        }

        public static void Loading()
        {
            HttpContext hc = HttpContext.Current;
            hc.Response.Write("<div id='loading'> ");
            hc.Response.Write("<img src='Images/Loading/loading.gif'/> ");
            hc.Response.Write("</div>");
            //hc.Response.Write("<script>mydiv.innerText = '';</script>");
            hc.Response.Write("<script type=text/javascript>");
            hc.Response.Write("function document.onreadystatechange()");
            hc.Response.Write(@"{ try  
                                   {
                                    if (document.readyState == 'complete') 
                                    {
                                         delNode('loading');
                                        
                                    }
                                   }
                                 catch(e)
                                    {
                                        alert('页面加载失败');
                                    }
                                                        } 

                            function delNode(nodeId)
                            {   
                                try
                                {   
                                      var div =document.getElementById(nodeId); 
                                      if(div !==null)
                                      {
                                          div.parentNode.removeChild(div);   
                                          div=null;    
                                          CollectGarbage(); 
                                      } 
                                }
                                catch(e)
                                {   
                                   alert('删除ID为'+nodeId+'的节点出现异常');
                                }   
                            }

                            ");

            hc.Response.Write("</script>");
            hc.Response.Flush();
        }