if (File.GetAttributes(FFName).ToString().IndexOf("ReadOnly") != -1)
 File.SetAttributes(FFName, FileAttributes.Normal);
 File.Delete(FFName);//不能刪除只讀文件

/// <summary>
    ///  用來遍歷刪除目錄下的文件以及該文件夾
    /// </summary>
    public void DeleteFileByDirectory(DirectoryInfo info)
    {
      foreach (DirectoryInfo newInfo in info.GetDirectories())
      {
        DeleteFileByDirectory(newInfo);
      }
      foreach (FileInfo newInfo in info.GetFiles())
      {
        newInfo.Attributes = newInfo.Attributes &~(FileAttributes.Archive | FileAttributes.ReadOnly | FileAttributes.Hidden);
        newInfo.Delete();
      }
      info.Attributes = info.Attributes & ~(FileAttributes.Archive | FileAttributes.ReadOnly | FileAttributes.Hidden);
      info.Delete();

    }