Multiple file-extensions searchPattern for System.IO.Directory.GetFiles

Question

var filteredFiles = Directory
    .GetFiles(path, "*.*")
    .Where(file => file.ToLower().EndsWith("aspx") || file.ToLower().EndsWith("ascx"))
    .ToList();

Edit 2014-07-23

You can do this in .NET 4.5 for a faster enumeration:

var filteredFiles = Directory
    .EnumerateFiles(path) //<--- .NET 4.5
    .Where(file => file.ToLower().EndsWith("aspx") || file.ToLower().EndsWith("ascx"))
    .ToList();

Directory.EnumerateFiles in MSDN

I believe there is no "out of the box" solution, that's a limitation of the Directory.GetFiles method.

It's fairly easy to write your own method though, here is an example.

The code could be:

/// <summary>
/// Returns file names from given folder that comply to given filters
/// </summary>
/// <param name="SourceFolder">Folder with files to retrieve</param>
/// <param name="Filter">Multiple file filters separated by | character</param>
/// <param name="searchOption">File.IO.SearchOption, 
/// could be AllDirectories or TopDirectoryOnly</param>
/// <returns>Array of FileInfo objects that presents collection of file names that 
/// meet given filter</returns>
public string[] getFiles(string SourceFolder, string Filter, 
 System.IO.SearchOption searchOption)
{
 // ArrayList will hold all file names
ArrayList alFiles = new ArrayList();

 // Create an array of filter string
 string[] MultipleFilters = Filter.Split('|');

 // for each filter find mathing file names
 foreach (string FileFilter in MultipleFilters)
 {
  // add found file names to array list
  alFiles.AddRange(Directory.GetFiles(SourceFolder, FileFilter, searchOption));
 }

 // returns string array of relevant file names
 return (string[])alFiles.ToArray(typeof(string));
}

I like this method, because it is readable and avoids multiple iterations of the directory:

var allowedExtensions = new [] {".doc", ".docx", ".pdf", ".ppt", ".pptx", ".xls", ".xslx"}; 
var files = Directory
    .GetFiles(folder)
    .Where(file => allowedExtensions.Any(file.ToLower().EndsWith))
    .ToList();

GetFiles can only match a single pattern, but you can use Linq to invoke GetFiles with multiple patterns:

FileInfo[] fi = new string[]{"*.txt","*.doc"}
    .SelectMany(i => di.GetFiles(i, SearchOption.AllDirectories))
    .ToArray();

See comments section here: http://www.codeproject.com/KB/aspnet/NET_DirectoryInfo.aspx

var filteredFiles = Directory
    .EnumerateFiles(path, "*.*") // .NET4 better than `GetFiles`
    .Where(
        // ignorecase faster than tolower...
        file => file.ToLower().EndsWith("aspx")
        || file.EndsWith("ascx", StringComparison.OrdinalIgnoreCase))
    .ToList();

• 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"

Or, it may be faster to split and merge your globs (at least it looks cleaner):

"*.ext1;*.ext2".Split(';')
    .SelectMany(g => Directory.EnumerateFiles(path, g))
    .ToList();

I fear you will have to do somthing like this, I mutated the regex from here.

var searchPattern = new Regex(
    @"$(?<=\.(aspx|ascx))", 
    RegexOptions.IgnoreCase);
var files = Directory.EnumerateFiles(path)
    .Where(f => searchPattern.IsMatch(f))
    .ToList();