递归获取文件夹中的每一个文件

 private List<DownLoadFile> mapDir(CloudFileInfo fileInfo, List<DownLoadFile> saveDatas)
        {
            List<CloudFileInfo> datas = getData(fileInfo._id);
            CloudFileInfo file = null;
            for (int i = 0, size = datas.Count(); i < size; i++)
            {
                file = datas[i];
                file.path = fileInfo.path + "/" + file.name;
                if (file.isDir == "1")
                {
                    mapDir(file, saveDatas);
                }
                else
                {
                    DownLoadFile downLoadFile = getDownLoadFile(file);
                    if (downLoadFile != null)
                    {
                        saveDatas.Add(downLoadFile);
                    }
                    else {
                        return null;
                    }
                }
            }
            return saveDatas;
        }