在gridview中嵌入checkbox,但无论我怎么选中，checkbox.checked = false,不知为什么

我明明在页面上选中了，但加断点走的时候发现checked都等于false 
<asp:GridView ID ="GrV_NewInspect" runat ="server" AllowPaging="True" AutoGenerateColumns="False" DataKeyNames ="qyid" OnSelectedIndexChanged="GrV_NewInspect_SelectedIndexChanged" OnPageIndexChanging="GridView1_PageIndexChanging"  OnSelectedIndexChanging="GrV_NewInspect_SelectedIndexChanging" Width="728px"  >
        <HeaderStyle  Height="18px" ForeColor="black" Font-Overline="False" HorizontalAlign="Center"/>
        <Columns >
        <asp:TemplateField >
            <ItemTemplate >
                    <asp:CheckBox ID="cbSelect" runat ="server" />
            </ItemTemplate>
            <ItemStyle Width ="3%" />
        </asp:TemplateField>
        <asp:TemplateField HeaderText="企业名称">
             <ItemTemplate>
                  <asp:LinkButton ID="LinkBn_CoName" runat="server" CommandName="select" Text='<%# Eval("qymc") %>'></asp:LinkButton>
             </ItemTemplate>
             <ItemStyle Width="270px" />
        </asp:TemplateField>
        <asp:BoundField DataField ="jcry" HeaderText ="检查人" SortExpression ="jcry" >
            <ItemStyle Width="70px" />
            <HeaderStyle Width="70px" />
        </asp:BoundField>
        <asp:BoundField DataField ="jctzsbh" HeaderText ="检查通知书编号" SortExpression ="jctzsbh" >
            <ItemStyle Width="100px" />
            <HeaderStyle Width="100px" />
        </asp:BoundField>
        <asp:BoundField DataField ="jcrq" HeaderText ="检查日期" SortExpression ="jcrq">
            <ItemStyle Width="100px" />
            <HeaderStyle Width="100px" />
        </asp:BoundField>
         <asp:TemplateField HeaderText="待上报数据" >
            <ItemTemplate>
                    <p style="color:#2D7384;">待上报数据</p>
            </ItemTemplate>
            <ItemStyle Width ="70px" />
        </asp:TemplateField>
        </Columns>
        <pagertemplate>
                    <table width="100%" id="pageC" >
                          <tr>
                            <td style="text-align:right;">
                                
                                第<asp:Label id="lblPageIndex" runat="server" text='<%# ((GridView)Container.Parent.Parent).PageIndex + 1  %>' />页
                                共<asp:Label id="lblPageCount" runat="server" text='<%# ((GridView)Container.Parent.Parent).PageCount  %>' />页 &nbsp;
                                <asp:linkbutton id="btnFirst" runat="server" causesvalidation="False" commandargument="First" commandname="Page" text="首页" />
                                <asp:linkbutton id="btnPrev" runat="server" causesvalidation="False" commandargument="Prev" commandname="Page" text="上一页" />
                                <asp:linkbutton id="btnNext" runat="server" causesvalidation="False" commandargument="Next" commandname="Page" text="下一页" />                          
                                <asp:linkbutton id="btnLast" runat="server" causesvalidation="False" commandargument="Last" commandname="Page" text="尾页" />                                            
                                <asp:textbox id="txtNewPageIndex" runat="server" width="20px" text='<%# ((GridView)Container.Parent.Parent).PageIndex + 1  %>' />
                                <asp:linkbutton id="btnGo" runat="server" causesvalidation="False" commandargument="-1" commandname="Page" text="GO" />&nbsp;
                             </td>
                          </tr>
                        </table>
          </pagertemplate>
    </asp:GridView> System.Text.StringBuilder sb = new System.Text.StringBuilder(" insert into inspect_dsb select QYID, QYMC, jctzsbh,jcmd,jcyj,jcnr,jcjl,jcry, 1,sysdate from inspect_tmp where");
        int n = 0;
        for (int i = 0; i < GrV_NewInspect.Rows.Count; i++)  //循环gridview一页中的每行,知道哪些行被选中
        {            GridViewRow row = GrV_NewInspect .Rows[i];
            CheckBox cbox = (CheckBox)row.FindControl("cbSelect");
            if (cbox.Checked == true)
            {
                n++;
                if (n == 1)
                {
                    sb.Append(" qyid=" + GrV_NewInspect.DataKeys[i].Value);
                }
                else
                {
                    sb.Append(" or qyid=" + GrV_NewInspect.DataKeys[i].Value);
                }
            }
        }
        if (n > 0)  //判断,如果有行被选中则执行删除
        {
            oracleHelper oh = new oracleHelper();
            string sql = sb.ToString();
            oh.RunSQLDirect(sql);
        }
        ph.delectTheSelected(GrV_NewInspect, "cbSelect", "inspect_tmp", "qyid");
        bindGrv(hf_search.Value, hf_fr.Value);
大家帮我看看我错在哪里，谢谢 ^_^