WCF REST 4.0 Authorization with Form Based Authentication (SetAuthCookie)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.Security;

namespace WcfRestService2
{
    public partial class Default : System.Web.UI.Page
    {
        protected void Page_Load(object sender, EventArgs e)
        {

            btnLogin.Click += new EventHandler(btnLogin_Click);
            btnLogout.Click += new EventHandler(btnLogout_Click);
            CheckUserIdentity.Click += new EventHandler(CheckUserIdentity_Click);
        }

        void CheckUserIdentity_Click(object sender, EventArgs e)
        {
            FormsIdentity formIdentity = HttpContext.Current.User.Identity as FormsIdentity;
            if (formIdentity != null && formIdentity.IsAuthenticated)
            {
                lblMessage.Text = "User is autheticated";
            }
            else
            {
                lblMessage.Text = "User not authenticated";
            }
        }

        void btnLogout_Click(object sender, EventArgs e)
        {
            FormsAuthentication.SignOut();
            lblMessage.Text = "Signed Out";
        }

        void btnLogin_Click(object sender, EventArgs e)
        {
            if (Membership.ValidateUser("admin4", "123456789"))
            {
                FormsAuthentication.SetAuthCookie("admin6", false);
                lblMessage.Text = "Signed In";
                
            }
            
        }
    }
}