Gridview排序不适用于标头模板

Question

在下面的代码中我有gridview当我尝试按升序或降序对其进行排序时，如果列有标题模板，则无法帮助我解决问题。

<asp:GridView Width="100%" runat="server" ID="dgIndent" AutoGenerateColumns="false" AllowSorting="true" OnSorting="dgIndent_Sorting" CssClass="mGrid" PagerStyle-CssClass="pgr">
    <AlternatingRowStyle BackColor="White" />
    <Columns>
        <asp:TemplateField HeaderText="Recommended Quantity" SortExpression="RecommentedQuantity" HeaderStyle-BackColor="#B0C4DE" ItemStyle-Width="200px" HeaderStyle-VerticalAlign="Top">
            <HeaderTemplate>
                <asp:Label ID="lblRecommendedQuantity" runat="server" Text="Recommended Quantity"></asp:Label>
                <br />
                <br />
                <asp:TextBox runat="server" onkeypress="return isNumberKey(event, false);" ID="txtRecommendedQuantity" AutoPostBack="true" Height="20px" BorderStyle="Solid" BorderColor="#6495ED" BackColor="#B0C4DE" Width="150px" OnTextChanged="txtItem_TextChanged"></asp:TextBox>
            </HeaderTemplate>
            <EditItemTemplate>
                <asp:TextBox ID="RecommentedQuantity_e" onkeypress="return isNumberKey(event, false);" runat="server" Text='<%#Eval("RecommentedQuantity") %>'></asp:TextBox>
            </EditItemTemplate>
            <ItemTemplate>
                <asp:Label ID="RecommentedQuantity_i" Style="word-wrap: normal; word-break: break-all;" runat="server"> </asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
    <HeaderStyle Font-Bold="True" ForeColor="White" Height="50px" BackColor="#B0C4DE" />
</asp:GridView>