void rw_Closed(object sender, EventArgs e)
        {
            RecordsWindow rw = (RecordsWindow)sender;

            FCBList.Remove(rw.FCB);
            rw.FCB.Closefile();
        }
        private void OpenFile(FileUserControl fuc)
        {
            try
            {
                if ((from i in FCBList
                     where i.GetFileDescription().FileName == fuc.DirEntry.FileName
                     select i).AsParallel().FirstOrDefault() != null)
                {
                    throw new Exception("Can't open file, already open.");// create only one FCB.
                }
                FCBList.Insert(0, Dsk.Openfile(fuc.DirEntry.FileName, MainWindow.User, "IO"));

                RecordsWindow rw = new RecordsWindow(FCBList[0]);
                rw.Closed += rw_Closed;
                subwindows.Insert(0, rw);
                rw.Show();
            }
            catch (Exception exp)
            {
                ErrorHandling.ShowError(exp.Message);
            }
        }