.NET 2.x Копирование файла, использования потока, и ошибка "Файл занят" - C#

static void copy_file (string old_file,string new_file)
        {
            int n = 0, numbytestoread = 0, numbytesread=0,progress_all=0;
            FileInfo olds=new FileInfo(old_file);
            FileInfo news=new FileInfo(new_file);
 
            try
            {
                using (FileStream old_stream = new FileStream(olds.Name, FileMode.Open, FileAccess.Read))
                {
                    numbytestoread = (int)olds.Name.Length;
                    numbytesread = 0;
                    byte[] bytes = File.ReadAllBytes(olds.Name);
                    progress_all = bytes.Length;
                    while (numbytestoread > 0)
                    {
                        n = old_stream.Read(bytes, 0, numbytestoread);
                        if (n == 0)
                        {
                            break;
                        }
                        numbytesread += n;
                        numbytestoread -= n;
                    }
                    numbytestoread = bytes.Length;
                    using (FileStream new_stream = new FileStream(news.Name, FileMode.Create, FileAccess.Write))
                    {
                        new_stream.Write(bytes, 0, numbytestoread);
                        Console.WriteLine("Progress: " + numbytestoread / progress_all + "%");
                        new_stream.Close();
                    }
                    old_stream.Close();
                }

            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message,"ОШИБКА",MessageBoxButtons.OK,MessageBoxIcon.Error);
            }
        }