如何在gridview asp.net中动态创建文本框的值

Question

我想计算具有textbox.text！= null且外部按钮单击的行，但是当我尝试row.findcontrol时，这里的null是我的代码

    <asp:GridView ID="GridViewCellNo" runat="server" AutoGenerateColumns="False" BorderStyle="None"
GridLines="None" OnRowDataBound="GridViewAddCellNumber_RowDataBound" ShowFooter="True"
ShowHeader="false">
<Columns>
<asp:TemplateField ItemStyle-Width="200px">
<ItemTemplate>
<asp:Label ID="LabelGVCellRowNo" runat="server" Text='<%#Eval("CellRowNumber")%>'
Visible="false"></asp:Label>
<asp:TextBox ID="TextBoxCellNo" runat="server" Text='<%#Eval("CellNumber")%>' Width="350px"></asp:TextBox>
                                                        <asp:RegularExpressionValidator ID="REVCellNumber" runat="server" ControlToValidate="TextBoxCellNo"
                                                            CssClass="ErroreMessage" Display="None" ErrorMessage="&lt;b&gt;Required Field Missing&lt;/b&gt;&lt;br /&gt;Please enter the phone number(digits only)."
                                                            SetFocusOnError="True" ValidationExpression="^[0-9]*$"></asp:RegularExpressionValidator>
                                                        <asp:ValidatorCalloutExtender ID="VCOE_REVPhoneNumber" runat="Server" HighlightCssClass="validatorCalloutHighlight"
TargetControlID="REVCellNumber">
</asp:ValidatorCalloutExtender>
 </ItemTemplate>
 <FooterTemplate>
 <asp:TextBox ID="TextBoxAddCellNum" runat="server" Width="350px"></asp:TextBox>                                                   
<asp:RegularExpressionValidator ID="REVCellNumber" runat="server" ControlToValidate="TextBoxAddCellNum"                                                     CssClass="ErroreMessage" Display="None" ErrorMessage="&lt;b&gt;Required Field Missing&lt;/b&gt;&lt;br /&gt;Please enter the phone number(digits only)."
SetFocusOnError="True" ValidationExpression="^[0-9]*$"></asp:RegularExpressionValidator>
<asp:ValidatorCalloutExtender ID="VCOE_REVPhoneNumber" runat="Server" HighlightCssClass="validatorCalloutHighlight"
TargetControlID="REVCellNumber">
</asp:ValidatorCalloutExtender>
</FooterTemplate>
 </asp:TemplateField>
 <asp:TemplateField FooterStyle-HorizontalAlign="left" ItemStyle-HorizontalAlign="left"
 ItemStyle-Width="200px" ShowHeader="False">                                        
 <FooterTemplate>
  <table>
  <tr>
 <td width="20px">
  </td>
<td>
 <asp:Button ID="addAttributeGridViewCellNoButtonAdd" runat="server" CausesValidation="true" Text="+" OnClick="GridViewAddCellNumberButtonAdd_Click" ToolTip="Add" ValidationGroup="AddCellNo" Width="30px" OnClientClick="showProgress()"  />
 </td>
  <td>
 Add another number
  </td>
  </tr>
  </table>
 </FooterTemplate>
  </asp:TemplateField>
  </Columns>
  </asp:GridView>

当我在按钮点击事件下面运行此功能时，它会给出txtCellno = null

private int GridViewCellNoCount()
    {
        int cellCount = 0;
        foreach (GridViewRow row in GridViewCellNo.Rows)
        {
            TextBox txtCellno = row.FindControl("TextBoxAddCellNum") as TextBox;

            //if (((TextBox)row.FindControl("TextBoxAddCellNum")).Text.Length > 0)
            if (txtCellno.Text.Length > 0)
            {
                cellCount++;
            }

        }
        return cellCount;