Return code or out parameter?

Question

I'm making a method to fetch a list of filenames from a server but I have come to a problem that I cannot answer.

The method returns two things:

• an SftpResult which is an enum with a variety of return codes.
• the list of filenames.

Of these three signatures:

public static ArrayList GetFileList(string directory, out SftpResult result)

public static SftpResult GetFileList(string directory, out ArrayList fileNames)

public static SftpFileListResult GetFileList(string directory)

(where SftpFileListResult is a composite object of an SftpResult and an ArrayList)

which is preferred and why?

Answer 1

Personally I prefer the last option (although using a List<T> or ReadOnlyCollection<T> instead of ArrayList). out parameters are basically a way of returning multiple values, and it's generally nicer to encapsulate those.

Another option in .NET 4 would be

Tuple<SftpResult, ArrayList> GetFileList(string directory)

That explicitly says, "this method returns two things... I've packed them together for you for this particular case, but it's not worth further encapsulating them: they're not worth composing in a separate type".

(If you're not using .NET 4 you could always write your own Tuple type.)