Utilities for walking through file systems

FileSystemExtensions.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;


public static class FileSystemExtensions
{
    /// <summary>
    /// Walks the file system, similar to Python's os.walk function.
    /// </summary>
    /// <param name="root">The root directory where the walking starts.</param>
    /// <param name="handler">A function that will be invoked for each directory.</param>
    /// <param name="searchRegex">A regular expression used to filter the list of files.  If a value is provided, <paramref name="searchPattern"/> will be ignored.</param>
    /// <param name="searchPattern">The search pattern used to limit the files and directories.</param>
    /// <param name="searchOption">Option to use when searching files and directories.</param>
    /// <param name="searchPatternAppliesToDirectories">Determines if the <paramref name="searchPattern"/> and <paramref name="searchOption"/> are used on only the files or both the files and directories.</param>
    /// <example><code>static void AddToFileList(DirectoryInfo root, DirectoryInfo[] directories, FileInfo[] files)
    /// {
    ///     foreach (var file in files)
    ///     {
    ///         Console.WriteLine(file.FullName);
    ///     }
    /// }
    /// 
    /// static void Main(string[] args)
    /// {
    ///     var root = new DirectoryInfo(@"C:\temp");
    ///     root.Walk(AddToFileList);
    /// }</code></example>
    public static void Walk(this DirectoryInfo root, Action<DirectoryInfo, IEnumerable<DirectoryInfo>, IEnumerable<FileInfo>> handler, Regex searchRegex = null,
        string searchPattern = null, SearchOption searchOption = SearchOption.AllDirectories, bool searchPatternAppliesToDirectories = false)
    {
        if (root == null)
        {
            throw new ArgumentNullException("directory");
        }
        IEnumerable<DirectoryInfo> directories = !searchPatternAppliesToDirectories || (searchRegex != null && searchPattern == null) ? root.EnumerateDirectories()
            : searchRegex != null ? root.EnumerateDirectories().Where(d => searchRegex.IsMatch(d.Name))
            : root.GetDirectories(searchPattern, searchOption);

        IEnumerable<FileInfo> files = searchRegex == null && searchPattern == null ? root.GetFiles()
            : searchRegex != null ? root.EnumerateFiles().Where(f => searchRegex.IsMatch(f.Name))
            : root.GetFiles(searchPattern, searchOption);

        handler.Invoke(root, directories, files);

        foreach (var d in directories)
        {
            d.Walk(handler, searchRegex, searchPattern, searchOption);
        }
    }
}