using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace TreeViewSample
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public MainWindow()
        {
            InitializeComponent();
            InitInstance();
        }

        private void InitInstance()
        {
            DriveInfo[] drives = DriveInfo.GetDrives();
            foreach (DriveInfo drive in drives)
            {
                trvStructure.Items.Add(CreateTreeItem(drive));
            }
        }

        private TreeViewItem CreateTreeItem(object obj)
        {
            TreeViewItem item = new TreeViewItem();
            item.Header = obj.ToString();
            item.Tag = obj;
            item.Items.Add("Loading...");
            return item;
        }

        private void trvStructure_Expanded(object sender, RoutedEventArgs e)
        {
            TreeViewItem item = e.Source as TreeViewItem;
            if (item.Items.Count != 1 || !(item.Items[0] is string))
                return;

            item.Items.Clear();
            DirectoryInfo expandedDir = null;
            if (item.Tag is DriveInfo)
                expandedDir = (item.Tag as DriveInfo).RootDirectory;
            if (item.Tag is DirectoryInfo)
                expandedDir = (item.Tag as DirectoryInfo);

            try
            {
                foreach (DirectoryInfo subDir in expandedDir.GetDirectories())
                    item.Items.Add(CreateTreeItem(subDir));
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }
    }
}