为什么会错？

.html
<%@ Page language="c#" Codebehind="list.aspx.cs" AutoEventWireup="false" Inherits="qwy.leaveWord.list" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
<HEAD>
<title>list</title>
<meta content="Microsoft Visual Studio 7.0" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
</HEAD>
<body MS_POSITIONING="GridLayout">
<form id="list" method="post" runat="server">
<FONT face="宋体">
<TABLE id="Table1" cellSpacing="1" cellPadding="1" width="740" border="0">
<TR>
<TD></TD>
</TR>
<TR>
<TD>
<TABLE id="Table2" cellSpacing="1" cellPadding="1" width="100%" border="0">
<TR>
<TD><asp:label id="Label7" runat="server" Width="373px"></asp:label></TD>
</TR>
<TR>
<TD></TD>
</TR>
<TR>
<TD><asp:datagrid id="dgfiList" runat="server" cellpadding="4" CellSpacing="1" Width="97%" BorderWidth="0px" AllowPaging="True" AutoGenerateColumns="False" HorizontalAlign="Center" PageSize="20">
<PagerStyle Visible="False"></PagerStyle>
<Columns>
<asp:TemplateColumn HeaderText="状态">
<HeaderStyle HorizontalAlign="Center" Width="25px"></HeaderStyle>
<ItemStyle HorizontalAlign="Center" VerticalAlign="Top" Width="25px"></ItemStyle>
<ItemTemplate>
<asp:Label ID="Id" Runat="server" Visible="False" Text='<%# DataBinder.Eval(Container, "DataItem.lWId") %>'>
</asp:Label>
<asp:Label ID="Pic" Runat="server">
<img src='image/Folder.gif' border='0'></asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="主 题(点&lt;img src='../images/Open.gif' border='0'&gt;即可展开贴子列表)">
<HeaderStyle HorizontalAlign="Center"></HeaderStyle>
<ItemStyle VerticalAlign="Top"></ItemStyle>
<ItemTemplate>
<asp:ImageButton ID="ImgOpen" ImageUrl="../images/Open.gif" BorderWidth="0" Width="16" Height="16" Runat="server" OnCommand="ImageButton_Command"></asp:ImageButton>
<asp:Label ID="Title" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.subject") %>'>
</asp:Label>
<asp:Label ID="Pageing" Runat="server"></asp:Label>
<asp:DataList ID="dlcdList" Runat="server" Width="100%" RepeatDirection="Vertical" RepeatLayout="Table" CellPadding="2" CellSpacing="1">
<ItemTemplate>
<img src="../images/Close.gif" border="0">
<asp:Label ID="Child" Runat="server"></asp:Label>
<asp:Label ID="cId" Runat="server" Visible="False" text='<%# DataBinder.Eval(Container, "DataItem.lWId") %>'>'></asp:Label>
<asp:Label ID="cTitle" Runat="server" Visible="False" text='<%# DataBinder.Eval(Container, "DataItem.subject") %>'>
</asp:Label>
<asp:Label ID="cUsers" Runat="server" Visible="False" text='<%# DataBinder.Eval(Container, "DataItem.userName") %>'>
</asp:Label>
</ItemTemplate>
</asp:DataList>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="作 者">
<HeaderStyle HorizontalAlign="Center" Width="80px"></HeaderStyle>
<ItemStyle HorizontalAlign="Center" VerticalAlign="Top" Width="80px"></ItemStyle>
<ItemTemplate>
<asp:label ID="Users" Runat="server" text='<%# DataBinder.Eval(Container, "DataItem.userName") %>'>
</asp:label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="回复/人气">
<HeaderStyle HorizontalAlign="Center" Width="80px"></HeaderStyle>
<ItemStyle HorizontalAlign="Center" VerticalAlign="Top" Width="80px"></ItemStyle>
<ItemTemplate>
<asp:Label ID="Revert" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.replyNum") %>'>
</asp:Label>
/
<asp:Label ID="Hit" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.clickNum") %>'>
</asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
<asp:TemplateColumn HeaderText="最后更新 | 回复人">
<HeaderStyle HorizontalAlign="Center" Width="175px"></HeaderStyle>
<ItemStyle VerticalAlign="Top" Width="175px"></ItemStyle>
<ItemTemplate>
&nbsp;
<asp:Label ID="RevertDate" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.editTime") %>'>
</asp:Label>
|
<asp:Label ID="RevertUsers" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.replyUserName") %>'>
</asp:Label>
</ItemTemplate>
</asp:TemplateColumn>
</Columns>
</asp:datagrid></TD>
</TR>
</TABLE>
</TD>
</TR>
</TABLE>
</FONT>
</form>
</body>
</HTML>
错误代码：输入字符串的格式不正确。 
说明: 执行当前 Web 请求期间，出现未处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.FormatException: 输入字符串的格式不正确。源错误: 
行 46：  {
行 47：  //Label Id=(Label)dgfiList.Items[Int32.Parse(e.CommandName)].FindControl("Id");
行 48：  Label Id=(Label)dgfiList.Items[Int32.Parse(e.CommandName)].FindControl("Id");
行 49： 
行 50：  //string Id = e.CommandName.Length.ToString();
 源文件: c:\inetpub\wwwroot\qwy\leaveword\list.aspx.cs    行: 48