使用OnPreRender 输出脚本

需要在前台输出一句脚本控制显示,我使用OnPreRender ,但发现输出在html页面
之前,会发生找不到对象的错误.
我看的范例是用于输出脚本函数,然后在页面触发脚本
http://dotnet.chinaitlab.com/ASPNET/39433.html

 1 
 2           #region  override OnPreRender   预生成 输出 HTML 脚本
 3 
 4           #region  override OnPreRender
 5           ///   <summary>
 6           ///  重载预生成方法,生成页面的描述边框内容
 7           ///   </summary>
 8           ///   <param name="e"></param>
 9           protected   override   void  OnPreRender(EventArgs e)
10          {
11               base .OnPreRender(e);
12               if  (ViewState[ " Edit " ]  != null )
13              {
14                  RenderJavaScript();
15                   this .ViewState[ " Edit " ]  =   null ;
16              }
17          }
18           #endregion
19 
20 
21           #region   脚本定义
22           private   const   string  SWITCH_SCRIPT_ID = " {29FD7A41-49FD-4fc4-AFA9-6A0B875A1A51} " ;
23 
24           private   const   string  SWITCH_SCRIPT = " <script language=\ " javascript\ " >\ndocument.getElementById(\ " GroupEdit\ " ).style.display=\ " \ " ;\n " +
25           " document.getElementById(\ " GroupList\ " ).style.display=\ " none\ " ;</script> " ;
26 
27           protected   void  RenderJavaScript()
28          {
29               if ( ! this .IsClientScriptBlockRegistered(SWITCH_SCRIPT_ID))
30              {
31                   this .RegisterClientScriptBlock(SWITCH_SCRIPT_ID, string .Format(SWITCH_SCRIPT, base .ID));
32              }
33 
34          }
35           #endregion
36 
37           #endregion
38