Can you call Directory.GetFiles() with multiple filters?

Question

I am trying to use the Directory.GetFiles() method to retrieve a list of files of multiple types, such as mp3\'s and jpg\'s. I have t

Answer 1

for

var exts = new[] { "mp3", "jpg" };

You could:

public IEnumerable FilterFiles(string path, params string[] exts) {
    return
        Directory
        .EnumerateFiles(path, "*.*")
        .Where(file => exts.Any(x => file.EndsWith(x, StringComparison.OrdinalIgnoreCase)));
}

• Don't forget the new .NET4 Directory.EnumerateFiles for a performance boost (What is the difference between Directory.EnumerateFiles vs Directory.GetFiles?)
• "IgnoreCase" should be faster than "ToLower" (.EndsWith("aspx", StringComparison.OrdinalIgnoreCase) rather than .ToLower().EndsWith("aspx"))

But the real benefit of EnumerateFiles shows up when you split up the filters and merge the results:

public IEnumerable FilterFiles(string path, params string[] exts) {
    return 
        exts.Select(x => "*." + x) // turn into globs
        .SelectMany(x => 
            Directory.EnumerateFiles(path, x)
            );
}

It gets a bit faster if you don't have to turn them into globs (i.e. exts = new[] {"*.mp3", "*.jpg"} already).

Performance evaluation based on the following LinqPad test (note: Perf just repeats the delegate 10000 times) https://gist.github.com/zaus/7454021

( reposted and extended from 'duplicate' since that question specifically requested no LINQ: Multiple file-extensions searchPattern for System.IO.Directory.GetFiles )