asp.net在页面提交时，显示提交中loading

<div id="doing" runat="server" >
<table width="100%" height="100%">
<tr align="middle" valign="center">
<td>
<table width="169" height="62" bgcolor="#99cccc" >
<tr align="middle" valign="center">
<td>页面提交中.<br>
loading.</td>
</tr>
</table>

</td>
</tr>
</table>
</div>

private void page_load(object sender, system.eventargs e)
  {
   // 在此处放置用户代码以初始化页面
   this.button1.attributes.add("onclick","javascript:document.getelementbyid('doing').style.visibility='visible';");
  
   }

override protected void onprerender(eventargs e)
  {
   doing.style.add("visibility","hidden");
  }