/// <summary>
        /// Returns the membership user's remaining locked out time.
        /// </summary>
        /// <param name="membershipUser">The membership user that this extension method affects.</param>
        /// <exception cref="ArgumentNullException"><paramref name="membershipUser"/> is <c>null</c>.</exception>
        public static TimeSpan RemainingLockedOutTime(this MembershipUser membershipUser)
        {
            if (membershipUser == null)
            {
                throw new ArgumentNullException("membershipUser");
            }

            return(membershipUser.IsLockedOut
                ? membershipUser.UnlockDate() - DateTime.Now
                : TimeSpan.Zero);
        }