Building a directory Structure

Question

My situation is that I am given a List which represents a directory structure, in the following format:

"My Folder\Images" "My Folder\Images\Gif" "My Folder\Images\JPG" "My Folder\Media" "My Folder\Media\Mov" "My Folder\Media\Mov\QT" "My Folder\Media\MPG"

There is no restriction on how many levels this can be nested.

I need to build something which represents a treeview from this, in the format:

public class Folder { public string FolderName { get; set; } public List<Folder> Folders{ get; set; } // a list of subfolders }

I just can't get the recrusive function which builds this quite right. Any help from the Gurus would be greatly appreciated.

TIA

Edit: My full class definition is:

public class Folder { public string Name { get; set; } public List<Folder> Folders { get; set; } public Folder(List<string> input) { foreach (var folder in input) { var delimPos = folder.IndexOf("\\"); if (delimPos == -1) { Name = folder ; } else { Name = folder.Substring(0, delimPos); var subFolders= input.Select(o => o.Substring(delimPos + 1)).ToList(); Folders= new List<Folder>(); foreach (var subFolder in subFolders) { Folders.Add(new Folder(new List<string>() { subFolder })); } } } } }

Share your recursive function. Lets see what is wrong with that — Pon Saravanan
– Pon Saravanan, Commented Jun 6, 2018 at 9:57
I am a bit confused now. Do you want to traverse a single string or a list of strings? — Pon Saravanan
– Pon Saravanan, Commented Jun 6, 2018 at 10:26
I wish to have each folder a name property and also a list of the subfolders it contains (and each subfolder to do the same). — Faithypop
– Faithypop, Commented Jun 6, 2018 at 10:33
Check out the non-recursive approach below and let me know if it works out for you. — vCillusion
– vCillusion, Commented Jun 6, 2018 at 13:34

CodeCaster · Accepted Answer · 2018-06-06 11:05:12Z

You of course have the problem that after splitting and processing Images\Gif, you're going to re-add another Images folder when splitting and processing Images\JPG. The first will have a Gif subfolder, the second will have a JPG subfolder.

You can fix this by grouping on the first part, and only processing the parts that follow:

public static List<Folder> ParseInputRecursive(string[] input) { var foldersInParts = input.Select(f => f.Split(new [] { '\\' }, StringSplitOptions.RemoveEmptyEntries).ToList()).ToList(); return ParseInputRecursive(foldersInParts); } public static List<Folder> ParseInputRecursive(List<List<string>> input) { var folders = new List<Folder>(); foreach (var folderPartsGroup in input.GroupBy(p => p[0])) { var folder = new Folder { Name = folderPartsGroup.Key }; // Remove parent name, skip parent itself var subFolders = folderPartsGroup.Select(f => f.Skip(1).ToList()).Where(f => f.Count > 0).ToList(); folder.Folders = ParseInputRecursive(subFolders); folders.Add(folder); } return folders; }

Printing them to verify:

// Sort to make sure parents always come first Array.Sort(input); var rootFolders = ParseInputRecursive(input); foreach (var folder in rootFolders) { PrintFoldersRecursive(folder); } public static void PrintFoldersRecursive(Folder folder, int depth = 0) { Console.WriteLine(new string('*', depth++) + folder.Name); foreach (var subFolder in folder.Folders) { PrintFoldersRecursive(subFolder, depth); } }

Given this input:

var input = new string[] { @"F1\Images", @"F1\Images\Gif", @"F1\Images\JPG", @"F1\Media", @"F1\Media\Mov", @"F2\Docs", @"F2\Docs\Foo", };

Gives this output:

F1 *Images **Gif **JPG *Media **Mov F2 *Docs **Foo

Pon Saravanan · Accepted Answer · 2018-06-06 10:45:40Z

For a simple node traversal by string parsing please refer the below example

private void button1_Click(object sender, EventArgs e) { var folders = ProcessNode("My Folder\\Media\\Mov\\QT", 0); MessageBox.Show("finished"); } private Folder ProcessNode(string input, int index) { var newIndex = input.IndexOf("\\", index + 1); if (newIndex < 0) return new Folder() { FolderName = input.Substring(index, input.Length - index) }; var nodeName = input.Substring(index, newIndex - index); var thisFolder = new Folder() { FolderName = nodeName, Folders = new List<Folder>() }; thisFolder.Folders.Add(ProcessNode(input, newIndex)); return thisFolder; }

If you want to use the split function and list

 private void button1_Click(object sender, EventArgs e) { var splitted = "My Folder\\Media\\Mov\\QT".Split('\\').ToList(); var foldersList = ProcessNode(splitted, 0); MessageBox.Show("finished"); } private Folder ProcessNode(List<string> input, int index) { if (index >= input.Count) return null; var thisFolder = new Folder() { FolderName = input[index], Folders = new List<Folder>() }; thisFolder.Folders.Add(ProcessNode(input, index + 1)); return thisFolder; }

vCillusion · Accepted Answer · 2018-06-07 07:45:54Z

Below is a non-recursive solution, it parses and prints the values as desired. Let me know if it helps. Demo

Logic

 public static IEnumerable<Folder> Parse(IEnumerable<string> locations) { var folders = new List<Folder>(); foreach (var location in locations) { var parts = location.Split(new[]{Path.DirectorySeparatorChar}, StringSplitOptions.RemoveEmptyEntries); Folder currentFolder = null; foreach (var part in parts) { var parentFolders = currentFolder!=null ? currentFolder.Folders : folders; currentFolder = parentFolders.Find(folder => folder.Name == part) ?? new Folder { Name = part }; if (!parentFolders.Any(folder => folder.Name.Equals(currentFolder.Name))) { parentFolders.Add(currentFolder); } } } return folders; }

Full Program

//Rextester.Program.Main is the entry point for your code. Don't change it. //Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5 using System; using System.IO; using System.Linq; using System.Collections.Generic; namespace Rextester { public class Folder { public string Name { get; set; } public List<Folder> Folders { get; internal set; } public Folder() { this.Folders = new List<Folder>(); } public static IEnumerable<Folder> Parse(IEnumerable<string> locations) { var folders = new List<Folder>(); foreach (var location in locations) { var parts = location.Split(new[]{Path.DirectorySeparatorChar}, StringSplitOptions.RemoveEmptyEntries); Folder currentFolder = null; foreach (var part in parts) { var parentFolders = currentFolder!=null ? currentFolder.Folders : folders; currentFolder = parentFolders.Find(folder => folder.Name == part) ?? new Folder { Name = part }; if (!parentFolders.Any(folder => folder.Name.Equals(currentFolder.Name))) { parentFolders.Add(currentFolder); } } } return folders; } public override string ToString() { if (this.Folders.Count == 0) { return this.Name; } else { var folders = this.Folders .SelectMany(folder => folder.ToString().Split(new[] { Environment.NewLine }, StringSplitOptions.None)) .Select(f => this.Name + Path.DirectorySeparatorChar + f); return string.Join(Environment.NewLine, folders); } } } public class Program { public static void Main(string[] args) { var locationList = new List<string>() { @"My Folder\Images", @"My Folder\Media", @"My Folder\Images\Gif", @"My Folder\Images\JPG", @"My Folder\Media\Mov", @"My Folder\Media\Mov\QT", @"My Folder\Media\MPG" }; var folderLists = Folder.Parse(locationList); Console.WriteLine(string.Join(Environment.NewLine, folderLists)); Console.ReadLine(); } } }

Output:

My Folder\Images\Gif My Folder\Images\JPG My Folder\Media\Mov\QT My Folder\Media\MPG

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