FormsAuthenticationService.cs

    public class FormsAuthenticationService : IFormsAuthenticationService
    {
        private readonly HttpContextBase _context;

        public FormsAuthenticationService(HttpContextBase context) {
            _context = context;
        }

        public void SignIn(string userName, bool createPersistentCookie, IEnumerable<string> roles = null) {
            string roleList = string.Empty;
            if (roles != null)
                roleList = string.Join(",", roles);

            var authTicket = new FormsAuthenticationTicket(
                1,
                userName,
                DateTime.Now,
                DateTime.Now.AddDays(30),
                createPersistentCookie,
                roleList,
                "/");

            var cookie = new HttpCookie(FormsAuthentication.FormsCookieName, FormsAuthentication.Encrypt(authTicket));

            if (authTicket.IsPersistent) {
                cookie.Expires = authTicket.Expiration;
            }

            _context.Response.Cookies.Add(cookie);
        }

        public void SignOut() {
            FormsAuthentication.SignOut();
        }
    }