GRIDVIEW里嵌套一个DetailsView，但是插入记录无法获取DetailsView里控件的值

GRIDVIEW里嵌套一个DetailsView，DetailsView是放在EmptyDataTemplate里面，我主要是想利用DetailsView来添加记录仅此而已。当点击GRIDVIEW里的添加链接就会链接到DetailsView，现在有一个问题，当我添加记录点击‘更新’出发DetailsView1_ItemInserting事件时如何获取DetailsView里模板的某一个控件的值？
前台代码如下：<asp:GridView ID="GVResult" >             <AlternatingRowStyle BackColor="White" />
             <Columns>
             <asp:BoundField DataField="Corse_Id" HeaderText="序号" ReadOnly="True" >
                 <HeaderStyle Width="30px" />
                 <ItemStyle HorizontalAlign="Center" />
                 </asp:BoundField>
                 <asp:BoundField DataField="Corse_Name" HeaderText="课程名称" >
                 <ControlStyle Font-Size="12px" Width="350px" />
                 </asp:BoundField>
                 <asp:TemplateField HeaderText="操作" ShowHeader="False">
                     <EditItemTemplate>
                         <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False" 
                             CommandName="Update" Text="更新"></asp:LinkButton>
                         &nbsp;<asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False" 
                             CommandName="Cancel" Text="取消"></asp:LinkButton>
                     </EditItemTemplate>
                     <ItemTemplate>
                         <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="False" 
                             CommandName="Edit" Text="编辑"></asp:LinkButton>
                         &nbsp;<asp:LinkButton ID="LinkButton2" runat="server" CausesValidation="False" 
                             CommandName="Delete" onclientclick=" javascript:return confirm('你确认要删除吗？')" 
                             Text="删除"></asp:LinkButton>
                         &nbsp;<asp:LinkButton ID="LinkButton3" runat="server" CausesValidation="False" 
                             CommandName="Insert" Text="添加"></asp:LinkButton>
                     </ItemTemplate>
                     <HeaderStyle Width="90px" />
                     <ItemStyle HorizontalAlign="Center" />
                 </asp:TemplateField>
             </Columns>             <EditRowStyle BackColor="#66CCFF" />
             <EmptyDataTemplate>
                 <asp:DetailsView ID="DetailsView1" runat="server" 
                    DefaultMode="Insert"  HeaderText="添加课程"  oniteminserting="DetailsView1_ItemInserting">
                     <Fields>
                         <asp:TemplateField HeaderText="Name">
                             <EditItemTemplate>
                                 <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
                             </EditItemTemplate>
                             <InsertItemTemplate>
                                 <asp:TextBox ID="TextBox1" runat="server" DataField="Corse_Name"></asp:TextBox>
                             </InsertItemTemplate>
                             <ItemTemplate>
                                 <asp:Label ID="Label1" runat="server"></asp:Label>
                             </ItemTemplate>
                         </asp:TemplateField>
                     </Fields>
                     <HeaderStyle/>
                     </asp:DetailsView>
             </EmptyDataTemplate>
             <FooterStyle Font-Bold="True" ForeColor="White" />
             <HeaderStyle BackColor="#CCCCFF" Font-Bold="False" Font-Size="12px" 
                 Height="30px" /> 
             <PagerStyle BackColor="#CCCCFF" ForeColor="Red" HorizontalAlign="Right" 
                 Font-Size="12px" Font-Strikeout="False" Font-Underline="True" />
             <RowStyle BackColor="#EFF3FB" />
             <SelectedRowStyle BackColor="#D1DDF1" Font-Bold="True" ForeColor="#333333" />
      </asp:GridView>后台代码：//获取GRIDVIEW控件里的DetailsView控件。
 
  DetailsView dv; protected void GVResult_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        if (e.Row.RowType == DataControlRowType.EmptyDataRow)
        {
            dv = e.Row.FindControl("DetailsView1") as DetailsView;           
        }         }//获取DetailsView控件里的TextBox1控件。这个地方出了错，提示“未将对象引用设置到对象的实例”
protected void DetailsView1_ItemInserting(object sender, DetailsViewInsertEventArgs e)
    {
        string name = ((TextBox)dv.FindControl("TextBox1")).Text.ToString().Trim();
     }请各位帮我看看？谢谢。