How to get hiddenfield in itemtemplate of gridview in button click

//........Server side code.........

protected void row_click(object sender, GridViewCommandEventArgs e)

    {

string hiddenFieldValue = ((HiddenField) grdname.Rows[0].FindControl("showfieldid")).Value;

or

string hiddenFieldValue = ((HiddenField)grdname.Rows[((GridViewRow)(((LinkButton)e.CommandSource).NamingContainer)).RowIndex].FindControl("showfieldid")).Value;

       

    }

//........Client side code.........

<asp:GridView ID="grdname" runat="server" AutoGenerateColumns="False" EmptyDataText="No data found" OnRowCommand="row_click">

                            <Columns>

                                <asp:TemplateField HeaderText="templateheader" ItemStyle-HorizontalAlign="left" Visible="true">

                                    <ItemTemplate>

                                        <asp:LinkButton ID="showfieldname" runat="server" Text=' <%# DataBinder.Eval(Container.DataItem, " showfield_name")%>'></asp:LinkButton>

                                        <asp:HiddenField ID="showfieldid" runat="server" Value=' <%# DataBinder.Eval(Container.DataItem, " showfield_id")%>'>

                                        </asp:HiddenField>

                                    </ItemTemplate>

                                </asp:TemplateField>

                            </Columns>

     </asp:GridView>