正在从模板字段内的控件中读取有界DataItem表达式文本

我有一个自定义的网格视图，在太多的页面中使用该网格，我想在后面的代码中为该网格内的所有列设置SortExpression文本；正如您在下面的代码中看到的那样，我通过重写OnRowDataBound事件处理程序来实现这一点。

问题是，我无法像在BoundField 中那样访问模板字段的评估数据字段表达式文本（在我的情况下为"START_WORK_DATE"）

<eska:GridView ID="gvEmployees" runat="server" CssClass="new-grid" PageSize="20"
    AllowSorting="true" AllowPaging="True" 
    AutoGenerateColumns="False" Width="100%"
    GridContainer="tdEmployees" DataKeyNames="ID" 
    RowHoverCssClass="HoverRow" ShowCheckBox="True"
    OnPageIndexChanging="gvEmployees_PageIndexChanging" 
    OnSelectedIndexChanged="gvEmployees_SelectedIndexChanged" 
    meta:resourcekey="gvEmployeesResource1">
    <PagerSettings FirstPageImageUrl="~/App_Themes/Images/First.gif" LastPageImageUrl="~/App_Themes/Images/last.gif"
        Mode="NextPreviousFirstLast" NextPageImageUrl="~/App_Themes/Images/Next.gif"
        PreviousPageImageUrl="~/App_Themes/Images/prev.gif"></PagerSettings>
    <SelectedRowStyle CssClass="SelectedRow"></SelectedRowStyle>
    <Columns>
        <asp:BoundField meta:resourcekey="BoundFieldResource1">
            <ItemStyle Width="2%" />
            <HeaderStyle Width="2%" />
            <FooterStyle Width="2%" />
        </asp:BoundField>
        <asp:BoundField  DataField="EMP_NO"  HeaderText="Employee No"
            meta:resourcekey="BoundFieldResource3">
            <HeaderStyle Width="10%"></HeaderStyle>
            <ItemStyle Width="10%"></ItemStyle>
            <FooterStyle Width="10%" />
        </asp:BoundField>
        <asp:BoundField DataField="NAME" HeaderText="Name"  meta:resourcekey="BoundFieldResource4">
            <HeaderStyle Width="34%"></HeaderStyle>
            <ItemStyle Width="34%"></ItemStyle>
            <FooterStyle Width="34%" />
        </asp:BoundField>
        <asp:TemplateField  HeaderText="Hiring Date"  meta:resourcekey="TemplateFieldResource1">
            <ItemTemplate>
<asp:Label runat="server"Text='<%# Convert.ToDateTime(DataBinder.Eval(Container,
"DataItem.START_WORK_DATE")).ToString("dd-MM-yyyy") %>'
                    ID="lblHiringDateGrid"></asp:Label>
            </ItemTemplate>
            <HeaderStyle Width="10%"></HeaderStyle>
            <ItemStyle Width="10%"></ItemStyle>
            <FooterStyle Width="10%" />
        </asp:TemplateField>
        <asp:BoundField DataField="PHONE1" HeaderText="Phone 1"
        meta:resourcekey="BoundFieldResource5">
            <HeaderStyle Width="10%"></HeaderStyle>
            <ItemStyle Width="10%"></ItemStyle>
            <FooterStyle Width="10%" />
        </asp:BoundField>
        <asp:BoundField DataField="Position_Name" HeaderText="Position"
        meta:resourcekey="BoundFieldResource6">
            <HeaderStyle Width="20%"></HeaderStyle>
            <ItemStyle Width="20%"></ItemStyle>
            <FooterStyle Width="20%" />
        </asp:BoundField>
        <asp:BoundField DataField="STATUS_DESC" HeaderText="Status"
        meta:resourcekey="BoundFieldResource7">
            <HeaderStyle Width="12%"></HeaderStyle>
            <ItemStyle Width="12%"></ItemStyle>
            <FooterStyle Width="12%" />
        </asp:BoundField>
        <asp:BoundField meta:resourcekey="BoundFieldResource8">
            <ItemStyle Width="2%" />
            <HeaderStyle Width="2%" />
            <FooterStyle Width="2%" />
        </asp:BoundField>
    </Columns>
</eska:GridView>

代码背后：

protected override void OnRowDataBound(GridViewRowEventArgs e)
    {
            if (e.Row.RowType == DataControlRowType.Header)
            {
                for (int i = 0; i < this.Columns.Count; i++)
                {
                    if (this.Columns[i] is BoundField)
                    {
                        if (((BoundField)(this.Columns[i])).DataField != string.Empty)
                        {
                            this.Columns[i].SortExpression = ((BoundField)(this.Columns[i])).DataField;
                        }
                    }
                    else if (this.Columns[i] is TemplateField)
                    {
                       // ???

                     }
                 }
             }

}

<asp:TemplateField>
        <HeaderTemplate>
            <asp:LinkButton ID="LinkButtonEmpName" runat="server" Text="Employee Name" CommandName="Sort" CommandArgument="Employees">
            </asp:LinkButton>
        </HeaderTemplate>
        <ItemTemplate>
            <asp:Label ID="LabelEmployee" runat="server" Text='<%# Bind("Employees") %>'/>
        </ItemTemplate>
        <FooterTemplate>
            <asp:TextBox ID="TextBoxEmployee" runat="server"/>
        </FooterTemplate>

protected void grd_RowCommand(object sender, GridViewCommandEventArgs e){
if (e.CommandName.Equals("Sort"))
{
    FilterExpression = e.CommandArgument.ToString() + " LIKE '%" + txtCaseNumber.Text + "%'";
    BindGridView();
}}