How do I display the Login and Logout links depending on if the user is logged in or not?

protected void LoginBtn_Click(object sender, EventArgs e)
        {
            if (userName.Text != "" && Password.Text != "")
            {
                //creates a connection to the database
                dbConnection = new OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0; Data Source=" +
                    Request.PhysicalApplicationPath + "App_Data\\Mercure.accdb");
                dbConnection.Open();

                string queryString = "SELECT * FROM LoginDetails WHERE Username = '" + userName.Text +
                    "' AND Password = '" + Password.Text + "'";

                try
                {
                    OleDbCommand cmd = dbConnection.CreateCommand();
                    cmd.CommandText = queryString;
                    OleDbDataReader dbReader = cmd.ExecuteReader();

                    if (dbReader.HasRows)
                    {
                        //setup cookies
                        HttpCookie loggedInCookie = new HttpCookie("LoggedIn", "true");
                        Response.Cookies.Add(loggedInCookie);

                        //username and password was correct and username being stored
                        Session["Username"] = userName.Text;
                        
                        if (userName.Text.StartsWith("EM"))
                        {
                            //move to employee page
                            Response.Redirect("employeeHome.aspx");
                        }
                        else
                        {
                            //move to client reservation page
                            Response.Redirect("Reservations.aspx");
                        }

                    }
                    else
                    {
                        LoginError.Text = "An incorrect username or password was entered!";
                    }
                }

                catch (Exception ex)
                {
                    LoginError.Text = "The following error occurred: " + ex.Message.ToString();
                }
                finally
                {
                    dbConnection.Close();
                }
            }
            else
            {
                LoginError.Text = "Please enter your details in the textboxes.";
            }
        }

namespace Mercure_Online_Booking
{
    public partial class SiteMaster : System.Web.UI.MasterPage
    {
        protected void Page_Load(object sender, EventArgs e)
        {
            //checks if cookies exists, and if the login value is true
            //if it does exist and is true, it enables the logout button
            if (Request.Cookies["LoggedIn"] != null
                && Request.Cookies["LoggedIn"].Value == "true")
            {
                logoutLinkBtn.Visible = true;
                LoginLinkBtn.Visible = false;
            }
            else if (Request.Cookies["LoggedIn"] != null
                && Request.Cookies["LoggedIn"].Value == "false")
            {
                logoutLinkBtn.Visible = false;
                LoginLinkBtn.Visible = true;
            }
        }

        protected void LoginLinkBtn_Click(object sender, EventArgs e)
        {
            Response.Redirect("Login.aspx");
        }

        protected void logoutLinkBtn_Click(object sender, EventArgs e)
        {
            if (Request.Cookies["LoggedIn"] != null)
            {
                HttpCookie myCookie = new HttpCookie("LoggedIn");
                myCookie.Expires = DateTime.Now.AddDays(-1);
                Response.Cookies.Add(myCookie);
                myCookie = null;
                HttpContext.Current.Session.Clear();
                Session.RemoveAll();
                HttpContext.Current.Session.Abandon();
            }
            
            Response.Redirect("Home.aspx");
        }

    }
}