How to filter Directory.EnumerateFiles with multiple criteria?

I have the following code:

List<string> result = new List<string>();

foreach (string file in Directory.EnumerateFiles(path,"*.*",  
      SearchOption.AllDirectories)
      .Where(s => s.EndsWith(".mp3") || s.EndsWith(".wma")))
       {
          result.Add(file);                 
       }

It works fine and does what I need. Except for one small thing. I would like to find a better way to filter on multiple extensions. I would like to use a string array with filters such as this:

string[] extensions = { "*.mp3", "*.wma", "*.mp4", "*.wav" };

What is the most efficient way to do this using NET Framework 4.0/LINQ? Any suggestions?

I'd appreciate any help being an occasional programmer :-)

Solution 1:

I created some helper methods to solve this which I blogged about earlier this year.

One version takes a regex pattern \.mp3|\.mp4, and the other a string list and runs in parallel.

public static class MyDirectory
{   // Regex version
   public static IEnumerable<string> GetFiles(string path, 
                       string searchPatternExpression = "",
                       SearchOption searchOption = SearchOption.TopDirectoryOnly)
   {
      Regex reSearchPattern = new Regex(searchPatternExpression, RegexOptions.IgnoreCase);
      return Directory.EnumerateFiles(path, "*", searchOption)
                      .Where(file =>
                               reSearchPattern.IsMatch(Path.GetExtension(file)));
   }

   // Takes same patterns, and executes in parallel
   public static IEnumerable<string> GetFiles(string path, 
                       string[] searchPatterns, 
                       SearchOption searchOption = SearchOption.TopDirectoryOnly)
   {
      return searchPatterns.AsParallel()
             .SelectMany(searchPattern => 
                    Directory.EnumerateFiles(path, searchPattern, searchOption));
   }
}

Solution 2:

Stripped from the LINQ context, this comes down to how to find out if a file matches a list of extensions. System.IO.Path.GetExtension() is a better choice here than String.EndsWith(). The multiple || can be replaced with .Contains() or .IndexOf() depending on the collection.

var extensions = new HashSet<string>(StringComparer.OrdinalIgnoreCase)  
   {  ".mp3", ".wma", ".mp4", ".wav" };

...  s => extensions.Contains(Path.GetExtension(s))