DataList、Repeater、GridView中的Checkbox取值问题

先看页面代码

<asp:DataList id="DataList1" runat="server" Width="100%" RepeatColumns="4" Font-Size="10pt">
        <ItemTemplate>
         <TABLE id="Table2" cellSpacing="0" cellPadding="0" width="100%" bgColor="gainsboro" border="0">
          <TR>
           <TD align="center">
            <asp:Label id=lblOName runat="server" Font-Size="10pt" Text='<%# DataBinder.eval_r(Container.DataItem,"nmenu_name")%>'>
            </asp:Label>
            <asp:Label id=lblID runat="server" Font-Size="10pt" Text='<%# DataBinder.eval_r(Container.DataItem,"nmenu_id")%>' Visible="False">
            </asp:Label></TD>
          </TR>
          <TR>
           <TD align="center">
            <asp:CheckBoxList id="cbSelect" runat="server" Font-Size="10pt" RepeatColumns="2" Width="100%" BackColor="#FFE0C0"
             RepeatDirection="Horizontal" DataTextField="nmenu_tname" DataValueField="nmenu_tid"></asp:CheckBoxList></TD>
          </TR>
         </TABLE>
        </ItemTemplate>
       </asp:DataList>

后台绑定CheckBox:

private void Page_Load(object sender, System.EventArgs e)
  {
   // 在此处放置用户代码以初始化页面
   if(!IsPostBack)
   {
    if(Session["UID"]!=null&&Session["UID"].ToString()!="")
    {
     BindList();
     BindCheckBox();
    }
    else
    {
     Server.Transfer("error.aspx");
    }
   }
  }
private void BindList()
  {
   string sql = "select * from NewsOne";
   DataList1.DataSource = ort.ExecuteToTable(sql);
   DataList1.DataBind();
  }
private void BindCheckBox()
  {
   foreach(DataListItem dli in DataList1.Items)
   {
    CheckBoxList cbl = (CheckBoxList)dli.FindControl("cbSelect");
    Label lbl = (Label)dli.FindControl("lblID");
    string sql = "select * from NewsTwo where nmenu_oid="+lbl.Text;
    cbl.DataSource = ort.ExecuteToTable(sql);
    cbl.DataBind();
   }
  }

CheckBox取值：

string list = "";
     foreach(DataListItem dli in DataList1.Items)
     {
      CheckBoxList cbSel = (CheckBoxList)dli.FindControl("cbSelect");
      for(int i=0;i<cbSel.Items.Count;i++)
      {
       if(cbSel.Items[i].Selected == true)
       {
        list += cbSel.Items[i].Value + ",";
       }
      }
     }
     list = list.Trim(",".ToCharArray());

有的时候会出现取不到值的情况，我的看法是缺少if(!IsPostBack)。