Is there a faster way than this to find all the files in a directory and all sub directories?

Question

I\'m writing a program that needs to search a directory and all its sub directories for files that have a certain extension. This is going to be used both on a local, and a

Answer 1

I'd be inclined to return an IEnumerable<> in this case -- depending on how you are consuming the results, it could be an improvement, plus you reduce your parameter footprint by 1/3 and avoid passing around that List incessantly.

private IEnumerable GetFileList(string fileSearchPattern, string rootFolderPath)
{
    DirectoryInfo di = new DirectoryInfo(rootFolderPath);

    var fiArr = di.GetFiles(fileSearchPattern, SearchOption.TopDirectoryOnly);
    foreach (FileInfo fi in fiArr)
    {
        yield return fi;
    }

    var diArr = di.GetDirectories();

    foreach (DirectoryInfo di in diArr)
    {
        var nextRound = GetFileList(fileSearchPattern, di.FullnName);
        foreach (FileInfo fi in nextRound)
        {
            yield return fi;
        }
    }
    yield break;
}

Another idea would be to spin off BackgroundWorker objects to troll through directories. You wouldn't want a new thread for every directory, but you might create them on the top level (first pass through GetFileList()), so if you execute on your C:\ drive, with 12 directories, each of those directories will be searched by a different thread, which will then recurse through subdirectories. You'll have one thread going through C:\Windows while another goes through C:\Program Files. There are a lot of variables as to how this is going to affect performance -- you'd have to test it to see.