CODEWITHSUNDEEP
c#.net
Alfie J. Palmer
Alfie J. Palmer

Reputation: 837

Fast I/O to check if directory contains files

I'm writing a C# application with .NET 4 to read and process data files (*.dat) from a list of directories.

Currently, I'm checking if a directory contains files using the following function:

    private bool FilesPresent()
    {
        string[] DIRS = Directory.GetDirectories(dataFileDirectoryPath, "*.*", SearchOption.TopDirectoryOnly);
        foreach (string d in DIRS)
        {
            string[] FILES = Directory.GetFiles(d, "*.*", SearchOption.AllDirectories);
            if (FILES.Length > 0) { return true; }
        }
        return false;                
    }

I've also tried some alternative solutions from the following post: How to quickly check if folder is empty (.NET)?

It's important to note that some of the directories have in excess of 1,000,000 files. Even reading the million+ file names into a string[] is taking a long time.

How can I implement this differently so that it runs faster?

Putting it simply; I'd just like to know the fastest way of checking if the directory is not empty. I'm not concerned with retrieving the filenames at this time.

Upvotes: 2

Views: 1284

Answers (2)

Tim Schmelter
Tim Schmelter

Reputation: 460048

Here's another approach using LINQ and EnumerateFileSystemEntries+AllDirectories:

bool noFiles = !Directory.EnumerateFileSystemEntries(dataFileDirectoryPath, "*.*", SearchOption.AllDirectories)
    .Any(entry => !File.GetAttributes(entry).HasFlag(FileAttributes.Directory));

If FileAttribute.HasFlag(FileAttributes.Directory) returns false it is a file.

Upvotes: 3

xanatos
xanatos

Reputation: 111830

Starting from .NET 4.0 there are two methods, EnumerateDirectories/EnumerateFiles that lazily enumerate directories/files.

private static bool FilesPresent()
{
    IEnumerable<string> dirs = Directory.EnumerateDirectories(dataFileDirectoryPath, "*.*", SearchOption.TopDirectoryOnly);
    foreach (string d in dirs)
    {
        IEnumerable<string> files = Directory.EnumerateFiles(d, "*.*", SearchOption.AllDirectories);
        if (files.Any()) { return true; }
    }
    return false;
}

Technically you could rewrite it as:

private static bool FilesPresent()
{
    IEnumerable<string> dirs = Directory.EnumerateDirectories(dataFileDirectoryPath, "*.*", SearchOption.TopDirectoryOnly);
    return dirs.Any(d => Directory.EnumerateFiles(d, "*.*", SearchOption.AllDirectories).Any());
}

But I do feel it would make it more unreadable.

Upvotes: 6

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