获取某行的字段ID值(GridView模板列)

aspx页面

<asp:GridView runat="server" ID="grd" AutoGenerateColumns="false" DataKeyNames="leagueID" OnRowCommand="grd_RowCommand"  OnRowCreated="grd_RowCreated">
<Columns>
<asp:TemplateField HeaderText="我要加入">
                    <ItemStyle HorizontalAlign="Center" />
                    <ItemTemplate>
                        &nbsp;<asp:Button runat="server" ID="btnJoin" Text="加 入" CommandName="btnJoin" />
                    </ItemTemplate>
                 </asp:TemplateField>
</Columns>
</asp:GridView>

aspx.cs类文件

 protected void grd_RowCommand(object sender, GridViewCommandEventArgs e)
    }