How to use Link button in Gridview

About.aspx=>
<%@ Page Title="About Us" Language="C#" MasterPageFile="~/Site.master" AutoEventWireup="true"
    CodeFile="About.aspx.cs" Inherits="About" %>
<asp:Content ID="HeaderContent" runat="server" ContentPlaceHolderID="HeadContent">
</asp:Content>
<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="MainContent">
        <div class="infobox" style="width: 700px; margin: 30px auto">
                <h2>
                    User Profile
                </h2>
                <div class="padding10">
                    <table cellspacing="0" border="0" cellpadding="8" style="width: 90%">
                        <tr>
                            <td align="right" style="width:160px">
                                Username:</td>
                            <td>
                                <asp:Label ID="lblUsername" runat="server"></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td align="right">
                                Gender:</td>
                            <td>
                                <asp:Label ID="lblSex" runat="server"></asp:Label></td>
                        </tr>
                        <tr>
                            <td align="right">
                                Age:</td>
                            <td>
                                <asp:Label ID="lblAge" runat="server"></asp:Label></td>
                        </tr>
                        <tr>
                            <td align="right">
                                Location:</td>
                            <td>
                                <asp:Label ID="lblLocation" runat="server"></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td align="right">
                                Occupation:</td>
                            <td>
                                <asp:Label ID="lblOccupation" runat="server"></asp:Label></td>
                        </tr>
                        <tr>
                            <td align="right">
                                Interests:</td>
                            <td>
                                <asp:Label ID="lblInterests" runat="server"></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td align="right">
                                Joined:</td>
                            <td>
                                <asp:Label ID="lblJoined" runat="server"></asp:Label>
                            </td>
                        </tr>
                        <tr>
                            <td align="right">
                                Last login:</td>
                            <td>
                                <asp:Label ID="lblLastLogin" runat="server"></asp:Label>
                            </td>
                        </tr>
                    </table>
                </div>
            </div>
</asp:Content>
About.aspx.cs=>
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Configuration;
public partial class About : System.Web.UI.Page
{
    SqlConnection con;
    string s = ConfigurationManager.ConnectionStrings["conn"].ToString();
    protected void Page_Load(object sender, EventArgs e)
    {
        con = new SqlConnection(s);
        SqlDataAdapter ad = new SqlDataAdapter("select * from Employees order by EmployeeID", con);
        string FirstName = "";
   if (this.Request.QueryString["FirstName"] == null)
   {
    return;
   }
            FirstName = Request.QueryString["FirstName"];
   DataSet ds = new DataSet();
            ad.Fill(ds);
   if (ds.Tables[0].Rows.Count == 0)
   {
    return;
   }
   DataRow row = ds.Tables[0].Rows[0];
 
   this.lblUsername.Text = row["FirstName"].ToString();
   this.lblLocation.Text = row["LastName"].ToString();
   this.lblOccupation.Text = row["Address"].ToString();
   this.lblLastLogin.Text = row["City"].ToString();
   this.lblJoined.Text = row["Region"].ToString();
            this.lblAge.Text = row["PostalCode"].ToString();
 
  }
    }