Search and List all files from directory/subdirectories into ListBox

Question

Ok solved a bit my old problem thx to @sircodesalot

Public Sub AppendFilesFromDirectory(ByVal path As DirectoryInfo, ByVal files As List(Of FileInfo)) For Each file As FileInfo In CurrentFolder.GetFiles() files.Add(file) Next For Each subfolder As DirectoryInfo In CurrentFolder.GetDirectories() AppendFilesFromDirectory(subfolder, files) Next End Sub

Dim files As New List(Of FileInfo) AppendFilesFromDirectory(New DirectoryInfo(FolderBrowserDialog1.SelectedPath), files) For Each file As FileInfo In files ListBox1.Items.Add(file.FullName) Next

And it works well for folders which have subfolders in it, but if a folder has only files then it becomes a loop adding continuously the file to myList.

Any suggestions how to avoid it? @sircodesalot kindly tried to explain me but I'm not able to do wathever I try..

Help is really appreciated!

Answer 1

First get your head around a simple recursive function like factorial. For example:

int factorial(int number) {
    if (number < 1)
        return 1;
    else
        return factorial(number - 1) * number;
}

Basically, if we want to calculate factorial(5), then it's just:

 factorial(5) * factorial(4) * factorial (3) * factorial(2) * factorial(1)

or more abstractly:

 factorial(n) * factorial(n - 1) * factorial (n - 2) * ... * factorial (1)

So we make the function call itself with a diminishing value to compute the result.

The same applies do your problem above. If we want to get all the sub directories, then all we have to do is:

(1) List all the files in the current folder
(2) For the files that are directories, repeat step one.

In other words:

List<Folder> readAllFiles() {
    List<Folder> folders = new List<Folder>();

    readAllFilesRecursively("C:/", folders);
}

List<Folder> readAllFilesRecursively(String directory, List<Folder> folders) {
     Folder currentDirectory = castTheStringToADirectorySomehow(directory);

     // Add the current folder to the list.
     folders.add(currentDirectory);


     // ** HERE IS WHAT YOU'RE MISSING ** //
     // Re-call the same function on the sub folder, passing in our list
     // so that the subfolder items can be added to the list.
     foreach (Folder subfolder in currentDirectory.subFolders()) {
          readAllFilesRecursively(subFolder.pathString(), folders);
     }

     // Return the folder list.
     return folders;
}

Edit:

So this works for me, but you'll have to change it to VB obviously. Also, I'm on a mac so you'll notice that the path format is a little different:

class Program {
    public static void Main() {

        List<FileInfo> files = new List<FileInfo> ();
        AppendFilesFromDirectory (new DirectoryInfo("/Users/sircodesalot/Desktop/Dev"), files);

        foreach (FileInfo file in files) {
            Console.WriteLine (file.FullName);
        }
    }

    public static void AppendFilesFromDirectory(DirectoryInfo currentFolder, List<FileInfo> files) {

        foreach (FileInfo file in currentFolder.GetFiles()) {
            files.Add(file);
        }

        // This if statement is unneccesary, but I'll add it for clarity 
        // to explain the concept of a base case. We don't really need it though
        // since the 'foreach' statement won't execute if there aren't any items.

        if (currentFolder.GetDirectories().Count() > 0) {

            // Process the subfolders
            foreach (DirectoryInfo subfolder in currentFolder.GetDirectories()) {
                AppendFilesFromDirectory (subfolder, files);
            }
        }
    }
}