datagrid模板列中添加LinkButton js报错

datagrid模板列中添加LinkButton js报错,而把LinkButton换成Button就没有问题
显示的错误是： 
行：      29 
字符：    3 
错误：    对象不支持此属性或方法 
代码：    0 
哪位高手帮小弟指点一下 这是页面代码 
<%@ Page language="c#" Codebehind="category_admin.aspx.cs" AutoEventWireup="false" Inherits="data.manager.category_admin" %> 
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > 
<HTML> 
   <HEAD> 
      <title>category_admin</title> 
      <meta name="GENERATOR" Content="Microsoft Visual Studio .NET 7.1"> 
      <meta name="CODE_LANGUAGE" Content="C#"> 
      <meta name="vs_defaultClientScript" content="JavaScript"> 
      <meta name="vs_targetSchema" content="http://schemas.microsoft.com/intellisense/ie5"> 
   </HEAD> 
   <body MS_POSITIONING="GridLayout"> 
      <form id="Form1" method="post" runat="server"> 
         <FONT face="宋体"></FONT> 
         <table width="100%" border="0" cellspacing="1" cellpadding="0"> 
            <tr> 
               <td colspan="2" align="center"><asp:DataGrid runat="server" id="DataGrid1" Height="120px" AutoGenerateColumns="False" BorderColor="#CCCCCC" 
                     BorderStyle="None" BorderWidth="1px" BackColor="White" CellPadding="4" GridLines="Horizontal" ForeColor="Black"> 
                     <SelectedItemStyle Font-Bold="True" ForeColor="White" BackColor="#CC3333"></SelectedItemStyle> 
                     <ItemStyle HorizontalAlign="Center"></ItemStyle> 
                     <HeaderStyle Font-Bold="True" HorizontalAlign="Center" ForeColor="White" BackColor="#0099FF"></HeaderStyle> 
                     <FooterStyle ForeColor="Black" BackColor="#CCCC99"></FooterStyle> 
                     <Columns> 
                        <asp:BoundColumn DataField="cindex" HeaderText="ID"></asp:BoundColumn> 
                        <asp:BoundColumn DataField="name" HeaderText="新闻标题"></asp:BoundColumn> 
                        <asp:TemplateColumn> 
                           <HeaderTemplate> 
                              <FONT face="宋体">状态</FONT> 
                           </HeaderTemplate> 
                           <ItemTemplate> 
                              <FONT face="宋体"> 
                                 <asp:Label id="lb_display" runat="server">Label</asp:Label></FONT> 
                           </ItemTemplate> 
                        </asp:TemplateColumn> 
                        <asp:TemplateColumn HeaderText="操作"> 
                           <HeaderTemplate> 
                              <FONT face="宋体">操作</FONT> 
                           </HeaderTemplate> 
                           <ItemTemplate> 
                              <FONT face="宋体"> 
                                 <asp:LinkButton id="modify" runat="server" CommandName="modify">修改</asp:LinkButton> 
                                 <asp:LinkButton id="delete" runat="server" CommandName="delete">删除</asp:LinkButton></FONT> 
                           </ItemTemplate> 
                        </asp:TemplateColumn> 
                     </Columns> 
                     <PagerStyle HorizontalAlign="Right" ForeColor="Black" BackColor="White"></PagerStyle> 
                  </asp:DataGrid> 
               </td> 
            </tr> 
            <tr> 
               <td width="50%" align="right">添加新类别：</td> 
               <td width="50%" align="left"><asp:TextBox ID="category" runat="server" /></td> 
            </tr> 
            <tr> 
               <td align="right">是否显示： 
               </td> 
               <td align="left"><asp:CheckBox ID="display" runat="server" /></td> 
            </tr> 
            <tr> 
               <td colspan="2" align="center"><asp:Button ID="submit" Text="添加" runat="server" /></td> 
            </tr> 
         </table> 
      </form> 
   </body> 
</HTML>