example22.cs

public class FormsAuthenticationService : IFormsAuthenticationService
    {
        public void SignIn(string userName, bool createPersistentCookie)
        {
            if (String.IsNullOrEmpty(userName)) throw new ArgumentException("Value cannot be null or empty.", "userName");
 
            FormsAuthentication.SetAuthCookie(userName, createPersistentCookie);
        }
 
        public void SignOut()
        {
            FormsAuthentication.SignOut();
        }
    }