C# Remove all empty subdirectories

Using C# Code.

static void Main(string[] args)
{
    processDirectory(@"c:\temp");
}

private static void processDirectory(string startLocation)
{
    foreach (var directory in Directory.GetDirectories(startLocation))
    {
        processDirectory(directory);
        if (Directory.GetFiles(directory).Length == 0 && 
            Directory.GetDirectories(directory).Length == 0)
        {
            Directory.Delete(directory, false);
        }
    }
}

If you can target the .NET 4.0 you can use the new methods on the Directory class to enumerate the directories in order to not pay a performance penalty in listing every file in a directory when you just want to know if there is at least one.

The methods are:

• Directory.EnumerateDirectories
• Directory.EnumerateFiles
• Directory.EnumerateFileSystemEntries

A possible implementation using recursion:

static void Main(string[] args)
{
    DeleteEmptyDirs("Start");
}

static void DeleteEmptyDirs(string dir)
{
    if (String.IsNullOrEmpty(dir))
        throw new ArgumentException(
            "Starting directory is a null reference or an empty string", 
            "dir");

    try
    {
        foreach (var d in Directory.EnumerateDirectories(dir))
        {
            DeleteEmptyDirs(d);
        }

        var entries = Directory.EnumerateFileSystemEntries(dir);

        if (!entries.Any())
        {
            try
            {
                Directory.Delete(dir);
            }
            catch (UnauthorizedAccessException) { }
            catch (DirectoryNotFoundException) { }
        }
    }
    catch (UnauthorizedAccessException) { }
}

You also mention that the directory tree could be very deep so it's possible you might get some exceptions if the path you are probing are too long.

Running the test on C:\Windows 1000 times on the 3 methods mentioned so far yielded this:

GetFiles+GetDirectories:630ms
GetFileSystemEntries:295ms
EnumerateFileSystemEntries.Any:71ms

Running it on an empty folder yielded this (1000 times again):

GetFiles+GetDirectories:131ms
GetFileSystemEntries:66ms
EnumerateFileSystemEntries.Any:64ms

So EnumerateFileSystemEntries is by far the best overall when you are checking for empty folders.