Have Directory.GetFiles return one file at a time? (.NET)

Question

I have a folder with far too many files in, and I want to go through each file one by one. The problem is that Directory.GetFiles returns a completed array, and this takes too long.

I would rather have an object I would point to a folder, then call a function that returns me the next file in the folder. Does .NET have a class like this please?

(I'd prefer to avoid win32 interops, as I plan to use this on Mono as well.)

Many thanks.

Thirtyone

Answer 1

You can't do this in .NET 3.5, but you can in .NET 4.0, as per this blog post:

DirectoryInfo directory = new DirectoryInfo(@"\\share\symbols");
IEnumerable<FileInfo> files = directory.EnumerateFiles();
foreach (var file in files) {
    Console.WriteLine("Name={0}, Length={1}", file.Name, file.Length);
}

(Likewise there's a static Directory.EnumerateFiles method.)

I don't know whether that API has been ported to Mono yet.

Chil

just a question, why not use: var files = directory.EnumerateFiles(); ? – Kaikaia

@Filip: I don't know about Jon's reasons, but I would use the type name for clarity since it is not obvious from the method name what type it returns. – Cod

@Fredrik, isn't it clear enough that it is going to return an enumeratable file info list? The Method-name is really self-explaining. The same goes for DirectoryInfo, i would rather use var directory =... I know that there is a difference at compile time though. – Kaikaia

@Fredrik: That example is copied directly from the referenced blog post. – Chil

Thanks. I was hoping for something that would work in .NET 2, but if it's not there, it's not there. (That's the second rule of Tuatology Club.) – Thirtyone

Answer 2

Take a look at FastDirectoryEnumerator project on CodeProject web site.

It does exactly what you need and even more, I was able to successfully use it on a slow network share with lots of files and performance was just great.

Drawback - it uses interop so it may not be portable to Mono.

Manipur

Thanks, I may end up using that, but falling back to Directory.GetFiles if it throws an interop exception, indicating that I'm probably not on win32. – Thirtyone

You can use Environment.OSVersion to determine if you are running under Windows or not and find some other code that will work fast on the operating system you are targeting. – Manipur