Problem showing folder structure in treeview

[OsheRono]

Ok, so here is my code

private void ChargerRep(TreeNodeCollection nodes, string rep)
        {
            //contruction de root
            TreeNode node = new TreeNode(rep);

            nodes.Add(node);

            string[] nom = System.IO.Directory.GetDirectories(rep);
            string[] fichiers = System.IO.Directory.GetFiles(rep);

            //on doit renommer le string repertoire, ou quelquechose qui resemble le string rep
            //pour eviter que le programme donne des erreurs. Comme le string fichiers est
            //initialisé dans la ligne de code string[] fichiers, ce nouveau variable montrera le
            //contenu des fichiers de l'arborescence, qui sont stockés dans le treenode (rep)
            foreach (string dir in nom)
            {
                string d = dir.Substring(dir.LastIndexOf(@"\") + 1);
                TreeNode noeud = new TreeNode(d);
                node.Nodes.Add(noeud);
            }
            
            
            foreach (string nomFichier in fichiers)
            {
                if (IsJpegImage(nomFichier))
                {
                    string nomF = nomFichier.Substring(nomFichier.LastIndexOf(@"\") + 1);
                    TreeNode noeud = new TreeNode(nomF);
                    node.Nodes.Add(noeud);
                }
            }

            //nodes.Add(node);
        }

Sorry if the comments in the code are in french. Ok what I am trying to do is to have the treeview list the chosen folder and the subfolders, with the corresponding jpeg files in each subfolder, if applicable. Problem is that while I can get the subfolders to show, they are just listed all first as a list, then the files are listed afterwards, as a list.

Here is the function using this one:

private void menuItemRepertoire_Click(object sender, EventArgs e)
        {
           
            //ouvreRepertoire.Rootfolder = Environment.SpecialFolder.Personal;
            if (ouvreRepertoire.ShowDialog() == DialogResult.OK)
            {
                //nettoie les donnees stockees pour l'utilisation
                arbreImages.Nodes.Clear();
                ChargerRep(arbreImages.Nodes, ouvreRepertoire.SelectedPath);

                //

            }
        }

I am quite lost trying to get it to list it by subfolder, any suggestions? Oh I tried DirectoryInfo, it only results in massive errors, I gave up trying to use it, although it seems nice, my teacher uses a weird coding technique...