gistfile1.txt

	public class EmailPreferencesLookup
	{
		public IEnumerable<NicknameToEmail> NicknamesToEmail { get; set; }
		public IEnumerable<FullNameToEmail> FullNamesToEmail { get; set; }
		public IEnumerable<EmailToEmailPreferences> EmailToPreferences { get; set; }

		public Maybe<EmailPreferences> GetPreferencesFor(string fullNameOrEmail)
		{
			var maybeNick = NicknamesToEmail.TryFind(
				x => x.Nickname == fullNameOrEmail,
				x => x.Email);

			var maybeFullName = FullNamesToEmail.TryFind(
				x => x.FullName == fullNameOrEmail,
				x => x.Email);

			return
				from email in maybeNick.Concat(maybeFullName)
				from prefs in EmailToPreferences.TryFind(
					x => x.Email == email,
					x => x.EmailPreferences).Value
				select prefs;
		}
	}

	internal static class EnumerableExtensions
	{
		public static Lazy<Maybe<TResult>> TryFind<T, TResult>(
			this IEnumerable<T> instance, Func<T, bool> predicate, Func<T, TResult> resultSelector)
			where T : class
		{
			if (instance == null)
			{
				return new Lazy<Maybe<TResult>>(() => Maybe<TResult>.None);
			}

			var found = instance.FirstOrDefault(predicate);
			return found != null
			       	? new Lazy<Maybe<TResult>>(() => Maybe.From(resultSelector(found)))
			       	: new Lazy<Maybe<TResult>>(() => Maybe<TResult>.None);
		}

		public static Maybe<T> Concat<T>(this Lazy<Maybe<T>> source1, Lazy<Maybe<T>> source2)
		{
			return source1.Value.IsNone
			       	? source2.Value
			       	: source1.Value;
		}
	}