This code loads the files and the directories of a directory into a treeview, here an example of how to use it

Code:
/*
 * Coded by Sam
 */
       private void Form1_Load(object sender, EventArgs e)
        {
            DirToTree("dirpath", treeViewVar);
        }

        public void DirToTree(string p, TreeView f, TreeNodeCollection c = null)
        {
            if (Directory.Exists(p))
            {
                if (c == null)
                    c = f.Nodes;

                foreach (string s in Directory.GetDirectories(p))
                {
                    if (new FileInfo(s).Attributes.HasFlag(FileAttributes.System)) continue;
                    c.Add(Path.GetFileName(s));
                    DirToTree(s, f, c[c.Count - 1].Nodes);
                }

                foreach (string s in Directory.GetFiles(p))
                {
                    if (new FileInfo(s).Attributes.HasFlag(FileAttributes.System)) continue;
                    c.Add(Path.GetFileName(s));
                }
            }
        }