кто-то разбирается в C# и потоках?

        public void WriteBack_DoWork(object sender, DoWorkEventArgs e)
        {
 
            for (int i = 0; i < IBlist.Count; i++)
            {
                Percentage = i;
               WriteBack.ReportProgress(Percentage);   //  <========================================
              if (Directory.Exists(AdresOfDB + "\\" + IBlist[i]) & Directory.Exists(USB))
                {
                    Directory.CreateDirectory(USB + IBlist[i]);
                    string[] files = Directory.GetFiles(AdresOfDB + "\\" + IBlist[i]);
                    foreach (string s in files)
                    {
                        string fileName = Path.GetFileName(s);
                        string destFile = Path.Combine(USB + IBlist[i], fileName);
                        File.Copy(s, destFile, true);
                    }
                }
            }
 
//            WriteBack.ReportProgress(Percentage);
            MessageBox.Show("Копирование завершено");
        }