C# read folder (names) from directory

You can use Directory.GetDirectories():

string[] subdirs = Directory.GetDirectories(fbd.SelectedPath);

This gives you the full paths to the subdirectories. If you only need the names of the subfolders, but not the full path, you can use Path.GetFileName():

string[] subdirs = Directory.GetDirectories(fbd.SelectedPath)
                            .Select(Path.GetFileName)
                            .ToArray();

Or if you want both:

var subdirs = Directory.GetDirectories(fbd.SelectedPath)
                            .Select(p => new {
                                Path = p,
                                Name = Path.GetFileName(p)})
                            .ToArray();

You need to use DirectoryInfo.GetDirectories.

using System;
using System.IO;

public class GetDirectoriesTest 
{
    public static void Main() 
    {

        // Make a reference to a directory.
        DirectoryInfo di = new DirectoryInfo("c:\\");

        // Get a reference to each directory in that directory.
        DirectoryInfo[] diArr = di.GetDirectories();

        // Display the names of the directories.
        foreach (DirectoryInfo dri in diArr)
            Console.WriteLine(dri.Name);
    }
}