My Personal Commander Variant

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Diagnostics;
using System.IO;
using System.Threading.Tasks;

namespace Lobster.FolderBrowser
{
    [System.ComponentModel.Composition.Export(typeof(IPathItemModel))]
    public class FolderFolderModel : FolderItemModelBase
    {
        public FolderFolderModel()
            : base(null, null)
        {
        }
        public FolderFolderModel(string _Pathname, FolderModelConfiguration conf)
            : base(_Pathname, conf)
        {
        }

        public override void UpdateDetails()
        {
            Debug.Assert(Directory.Exists(pathname));

            FileSize = long.MinValue; // Signals the ui the filesize will be shown as an empty string

            DirectoryInfo di = new DirectoryInfo(pathname);
            Attributes = di.Attributes;
            CreationTime = di.CreationTime;
            ChangeTime = di.LastWriteTime;

            if ((configuration != null) && (configuration.CalculateFolderSizes))
            {
                Task t = new Task(() =>
                {
                    var r = GetFolderSize(pathname);
                    long l = r.Item2 ? -r.Item1 : r.Item1;
                    if ((r.Item1 == 0) && (r.Item2 == true)) l = long.MaxValue;

                    FileSize = l;
                });

                t.Start();
            }
        }

        // see http://stackoverflow.com/questions/468119/whats-the-best-way-to-calculate-the-size-of-a-directory-in-net
        private static Tuple<long, bool> GetFolderSize(string folder)
        {
            long folderSize = 0;
            bool isIncomplete = false;
            try
            {
                if (!Directory.Exists(folder)) return new Tuple<long, bool>(0, true);

                try
                {
                    foreach (string file in Directory.GetFiles(folder))
                    {
                        if (File.Exists(file))
                        {
                            FileInfo finfo = new FileInfo(file);
                            folderSize += finfo.Length;
                        }
                    }

                    foreach (string dir in Directory.GetDirectories(folder))
                    {
                        var r = GetFolderSize(dir);
                        folderSize += r.Item1;
                        isIncomplete |= r.Item2;
                    }
                }
                catch (Exception)
                {
                    isIncomplete = true;
                }
            }
            catch (Exception)
            {
                isIncomplete = true;
            }
            return new Tuple<long, bool>(folderSize, isIncomplete);
        }

        public override string NameID { get { return "Folder"; } }
    }
}