使Detailview字段不可见和可访问

我有一个databounddetailsviewcontrol。用于显示一些问题和答案选项以及正确答案

  <asp:DetailsView ID="DetailsView1" runat="server" AutoGenerateRows="False" 
                    BackColor="White" BorderColor="#999999" BorderStyle="Solid" BorderWidth="1px" 
                    CellPadding="3" DataSourceID="SqlDataSource1" GridLines="Vertical" 
                    Height="50px" Width="477px" ForeColor="Black">
                    <AlternatingRowStyle BackColor="#CCCCCC" />
                    <EditRowStyle BackColor="#000099" Font-Bold="True" ForeColor="White" />
                    <Fields>
                        <asp:BoundField DataField="Question" HeaderText="Question" 
                            SortExpression="Question" />
                        <asp:BoundField DataField="Answer 1" HeaderText="Answer 1" 
                            SortExpression="Answer 1" />
                        <asp:BoundField DataField="Answer 2" HeaderText="Answer 2" 
                            SortExpression="Answer 2" />
                        <asp:BoundField DataField="Answer 3" HeaderText="Answer 3" 
                            SortExpression="Answer 3" />
                        <asp:BoundField DataField="Answer 4" HeaderText="Answer 4" 
                            SortExpression="Answer 4" />
                        <asp:BoundField   DataField="Correct Answer" HeaderText="Correct"
                          SortExpression="Correct Answer" >
                        <FooterStyle BorderColor="White" />
                        </asp:BoundField>
                        <asp:BoundField DataField="Id" SortExpression="Id" />
                    </Fields>
                    <FooterStyle BackColor="#CCCCCC" />
                    <HeaderStyle BackColor="Black" Font-Bold="True" ForeColor="White" />
                    <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
                </asp:DetailsView>

但是我想对用户隐藏正确的答案字段，我试图使CorrectAnswer字段对设计师不可见，我成功了，但我的问题是当我试图读取不可见字段

的值时

a.CorrectAnswer = DetailsView1.Rows[5].Cells[1].Text;

我从不可见的详细信息视图字段

获得空字符串作为值

谁能建议任何方法使一个字段不可见，但保持值可访问的代码后面

CssClass="invisible"

.invisible {
    display:none;
}