小编roc*_*ker的帖子

嗨,我有一个aspx页面,其中我有以下代码

  <asp:ScriptManager ID="scriptManager" runat="server" AsyncPostBackTimeout="500" EnablePageMethods="true">
            </asp:ScriptManager>

            <script type="text/javascript">
          Sys.Application.add_init(BeginRequestHandler);
          Sys.Application.add_init(EndRequestHandler);

          Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequestHandler);
          Sys.WebForms.PageRequestManager.getInstance().add_endRequest(EndRequestHandler);
          function BeginRequestHandler(sender, args) {
              AsynProcessing('block', 'AlertDiv', 'ProcessingImage');
          }
          function EndRequestHandler(sender, args) {
              AsynProcessing('none', 'AlertDiv', '');
          }
          function AsynProcessing(visstring, elem, img) {
              var adiv = $get(elem);
              adiv.style.display = visstring;
              adiv.image = img;
          }

但是该页面抛出了一个javascrip错误,因为'Sys.WebForms.PageRequestManager'为null或不是对象.我在scriptmanager标签下面放了.我甚至还说道

<xhtmlConformance  mode="Transitional"/>

在web.config.But部分仍然得到相同的错误.
任何帮助深表感谢.提前致谢