C#

/// <summary>
/// Returns a list of files from a directory
/// </summary>
/// <param name="files">A list of files</param>
/// <param name="directory">The directory in which to search</param>
/// <param name="filters">The file extension filters (separate by [,;|])</param>
/// <param name="recurse">Recurse through subdirectories</param>
private void AddFilesRecursively(List<FileInfo> files, DirectoryInfo directory,
                                 string filters, bool recurse)
{
    FileInfo[] dirFiles = directory.GetFiles("*.*", SearchOption.TopDirectoryOnly);
    if (filters == "*.*")
        files.AddRange(dirFiles);
    else
    {
        foreach (FileInfo file in dirFiles)
        {
            if (Regex.IsMatch(file.Extension, filters, RegexOptions.IgnoreCase))
                files.Add(file);
        }
    }
 
    if (recurse)
    {
        DirectoryInfo[] dirInfos = directory.GetDirectories();
        foreach (DirectoryInfo dir in dirInfos)
        {
            AddFilesRecursively(files, dir, filters, recurse, level+1);
        }
    }
}
 
/// <summary>
/// Returns an array of files from a directory
/// </summary>
/// <param name="path">The path in which to search</param>
/// <param name="filters">The regular expression by which to filter files by extension 
/// (or *.* for all files)</param>
/// <param name="recurse">Recurse through subdirectories</param>
/// <returns>An array of files</returns>
private List<FileInfo> GetFiles(string path, string filters, bool recurse)
{
    List<FileInfo> files = new List<FileInfo>();
 
    DirectoryInfo dirInfo = new DirectoryInfo(path);
    AddFilesRecursively(files, dirInfo, filters, recurse, 0);
 
    return files;
}