Create Logout page through session veriables

*These namespaces are must be required for SqlServer Connectivity in your web form:-

using System.Data;

using System.Data.SqlClient;

using System.Configuration;

ShowAllData.aspx

<%@ Page Title="" Language="C#" MasterPageFile="~/Site.Master" AutoEventWireup="true" CodeBehind="ShowAllData.aspx.cs" Inherits="ShowDataOnePage2010.ShowAllData" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder2" runat="server">

    <table style="width: 28%">

        <tr>

            <td style="width: 54px">

                <asp:LinkButton ID="LinkButtonLogout" runat="server" Font-Bold="True"

                    ForeColor="Maroon" onclick="LinkButtonLogout_Click">Logout</asp:LinkButton>

            </td>

        </tr>

    </table>

</asp:Content>

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server">

    <table style="width: 100%">

        <tr>

            <td>

                <asp:GridView ID="GridView1" runat="server" CellPadding="4" ForeColor="#333333"

                    GridLines="None" PageSize="5">

                    <AlternatingRowStyle BackColor="White" />

                    <EditRowStyle BackColor="#7C6F57" />

                    <FooterStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />

                    <HeaderStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />

                    <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" />

                    <RowStyle BackColor="#E3EAEB" />

                    <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />

                    <SortedAscendingCellStyle BackColor="#F8FAFA" />

                    <SortedAscendingHeaderStyle BackColor="#246B61" />

                    <SortedDescendingCellStyle BackColor="#D4DFE1" />

                    <SortedDescendingHeaderStyle BackColor="#15524A" />

                </asp:GridView>

            </td>

        </tr>

    </table>

</asp:Content>

<asp:Content ID="Content3" ContentPlaceHolderID="ContentPlaceHolder3" runat="server">

</asp:Content>

Web.Config File

<?xml version="1.0"?>

<configuration>

  <appSettings>

    <add key="ConnectionString" value="Server=PRADEEP-HP;Database=Decofloore2;User Id=User_006;password=user006"/>

   </appSettings>

</configuration>

ShowAllData.aspx.cs Page

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;

namespace ShowDataOnePage2010

{

    public partial class ShowAllData : System.Web.UI.Page

    {

        protected void Page_Load(object sender, EventArgs e)

        {

            if (Session["UserName"] == null)

            {

                Response.Redirect("~/LoginSingleData.aspx");

            }

            string StrCon = ConfigurationManager.AppSettings["ConnectionString"];

            SqlConnection SqlConn = new SqlConnection(StrCon);

            string StrSql = null;

            StrSql = "Select UserId,UserName,Address,PhoneNumber,State,City,Email,DateOfPurchasing,DateOfDelivery from Registration";// where UserName='" + UserName + "'";

            SqlCommand SqlComm = new SqlCommand(StrSql, SqlConn);

            SqlConn.Open();

            SqlDataReader dr;

            dr = SqlComm.ExecuteReader();

            GridView1.DataSource = dr;

            GridView1.DataBind();

            SqlConn.Close();

        }

Logout Button  

protected void LinkButtonLogout_Click(object sender, EventArgs e)

        {

            Session.Abandon();

            Session.Clear();

            Session.Remove("UserName");

            Session.RemoveAll();

            Response.Redirect("~/LoginSingleData.aspx");

        }

    }

}

https://www.youtube.com/channel/UCKLRUr6U5OFeu7FLOpQ-FSw/videos