datagrid与自定义验证问题。

[elby]

我自定一个验证控件，用来验证datagrid的更新字段，
但总提示更新字段的控件没有定义。

<asp:DataGrid AutoGenerateColumns="false" Visible="true" ID="datagrid1" runat="server" PageSize="20" PagerStyle-Mode="nextprev" PagerStyle-NextPageText="下一页"
PagerStyle-PrevPageText="上一页" AllowPaging="true" HeaderStyle-BackColor="#666666" HeaderStyle-ForeColor="#FFFFFF" AlternatingItemStyle-BackColor="#999999"
ItemStyle-BackColor="#FFFFFF" BorderColor="#000066" CellPadding="1" HeaderStyle-HorizontalAlign="center" ItemStyle-HorizontalAlign="center"
HorizontalAlign="Center" HeaderStyle-Font-Bold="true" BorderStyle="Solid" DataKeyField="id" Width="600"
OnPageIndexChanged="datagrid_pageindexchanged" OnCancelCommand="datagrid_cancelcommand" OnEditCommand="datagrid_editcommand"
OnUpdateCommand="datagrid_updatecommand" EnableViewState="true" OnDeleteCommand="datagrid_delete">
<columns>
<asp:BoundColumn DataField="powername" HeaderText="名称" />
<asp:BoundColumn DataField="powerno" HeaderText="排序" />
<asp:TemplateColumn HeaderText="权限" >
<itemtemplate>
<asp:BoundColumn DataField="userpower" HeaderText="权限" />
</itemtemplate>
<edititemtemplate>
<asp:ListBox BackColor="#CCCCCC" Font-Size="9" ForeColor="#990033"
Height="110" ID="editlist" Rows="9" runat="server" SelectionMode="multiple" Width="90">
<asp:ListItem Value="用户管理">用户管理</asp:ListItem>
<asp:ListItem Value="系统设置">系统设置</asp:ListItem>
<asp:ListItem Value="文件传输">文件传输</asp:ListItem>
<asp:ListItem Value="发布通报">发布通报</asp:ListItem>
<asp:ListItem Value="系统管理">系统管理</asp:ListItem>
<asp:ListItem Value="阅读文件">阅读文件</asp:ListItem>
</asp:ListBox>
</edititemtemplate>
</asp:TemplateColumn>
<asp:EditCommandColumn EditText="修改" CancelText="取消" UpdateText="更新" HeaderText="修改" />
<asp:buttoncolumn commandname="delete" HeaderText="删除" Text ="删除" />
</columns>
</asp:DataGrid><asp:CustomValidator runat="server" ID="vallist" ControlToValidate="editlist" OnServerValidate="checklist" />

........

sub checklist(sender as object,e as servervalidateeventargs)
dim listnum as integer
dim resultlist as boolean
for listnum=0 to editlist.items.count-1
if editlist.items(listnum).text="阅读文件" then '''总提示editlist 没有定义。如何处理。
resultlist=true
else
resultlist=false
end if
next
if resultlist=false then
e.isvalid=false
sender.errormessage="<font colo=red>阅读文件</font>必须选上!!!"
end if
end sub