获取不到Repeater控件中的CheckBox选中状态

写在前面的话：在做一个项目的时候，需要使用到Repeater控件，并且在Repeater控件内放置了CheckBox控件来标志需要删除的行，选中后，在后台取到的CheckBox的值总是为false。最后发现是在PageLoad函数中没有判断是否是回发就绑定了Repeater控件的数据，那么每次进入页面CheckBox控件的值当然被刷新为false了。

前台页面：

 <div class="contianer p10">
         <h3>
             当前位置：<a href="Index.aspx" target="_self" >首页</a>>文章管理</h3>
         <hr/>
         <div class="content">
                 <asp:repeater ID="rptArticle" runat="server" ClientIDMode="Static" >
                 <HeaderTemplate>
                 <table border="0" cellspacing="0" cellpadding="0" width="100%">
                     <tr>
                         <th width="6%">选择</th>
                         <th width="6%">编号</th>
                         <th align="left">文章标题</th>
                         <th width="16%">发布时间</th>
                         <th width="10%">操作</th>
                     </tr>
                     </HeaderTemplate>
                     <ItemTemplate>
                         <tr>
                             <td><asp:CheckBox ID="cb_id" CssClass="checkall" runat="server" /></td>
                             <td><asp:Label ID="lb_id" runat="server" Text='<%#Eval("aNo")%>'></asp:Label></td>
                             <td><a href="ArticleShow.aspx?id=<%#Eval("aNo") %>"><%#Eval("aTitle")%></a></td>
                             <td><%#string.Format("{0:g}", Eval("aDate"))%></td>
                             <td><span><a href="ArticleShow.aspx?id=<%#Eval("aNo") %>">修改</a></span></td>
                         </tr>
                     </ItemTemplate>
                     <FooterTemplate>
                     </table>
                     </FooterTemplate>
                 </asp:repeater>
         </div>
         <div class="clear"></div>
           <!-- 分页控件 -->
           <div>
             <webdiyer:AspNetPager ID="AspNetPager1" runat="server" HorizontalAlign="Right" ShowCustomInfoSection="Right"
                 Width="100%" Style="font-size: 12px" inputboxstyle="width:19px" CustomInfoHTML=""
                 ShowPageIndexBox="Always" AlwaysShow="false" FirstPageText="首页" LastPageText="尾页"
                 NextPageText="下一页" PrevPageText="上一页" CustomInfoStyle="FONT-SIZE: 12px" CurrentPageButtonClass="pagination"
                 PageSize="16" ForeColor="#1460AD" OnPageChanged="AspNetPager1_PageChanged">
             </webdiyer:AspNetPager>
           </div>
           <!-- 分页控件end -->

         <br />
         <asp:Button ID="BtnDelete" runat="server"
         OnClientClick="return confirm( '确定要删除这些记录吗？ ');"
         onclick="BtnDelete_Click" Text="删除" />
     &nbsp;
         <asp:Label ID="lbMsg" runat="server" Text=""></asp:Label>
         &nbsp;
         <asp:Button ID="BtnAdd" runat="server" Text="添加"
             onclick="BtnAdd_Click"/>

     </div>

后台页面：

 ArticleBLL bll = new ArticleBLL();
         protected void Page_Load(object sender, EventArgs e)
         {
             this.lbMsg.Text = "";
             if (!IsPostBack)
             {
                 BindRepeater();
             }
         }
         // 绑定数据
         private void BindRepeater()
         {
             string strSql = "select * from article";

             PagedDataSource ps = new PagedDataSource();
             ps.DataSource = bll.GetDataList(strSql).DefaultView;
             AspNetPager1.RecordCount = ps.Count;
             ps.CurrentPageIndex = AspNetPager1.CurrentPageIndex - ;
             ps.AllowPaging = true;
             ps.PageSize = AspNetPager1.PageSize;
             this.rptArticle.DataSource = ps;
             this.rptArticle.DataBind();
         }
         // 分页控件事件绑定
         public void AspNetPager1_PageChanged(object sender, EventArgs e)
         {
             BindRepeater();
         }
         // 添加文章
         protected void BtnAdd_Click(object sender, EventArgs e)
         {
             Response.Redirect("ArticleShow.aspx");
         }
         // 删除
         protected void BtnDelete_Click(object sender, EventArgs e)
         {
             for (int i = ; i < rptArticle.Items.Count; i++)
             {
                 int id = Convert.ToInt32(((Label)rptArticle.Items[i].FindControl("lb_id")).Text);
                 CheckBox cb = (CheckBox)rptArticle.Items[i].FindControl("cb_id");
                 if (cb.Checked)
                 {
                     bll.Delete(id.ToString());
                 }
             }
             this.lbMsg.Text = "删除成功";
         }

处理办法是在PageLoad里面判断是否是回发就可以了。