统计文件夹大小

private long GetFilesSize(String path)
        ...{
            DirectoryInfo directoryInfo = new DirectoryInfo(path);
            long length = 0;
            foreach (FileSystemInfo fsi in directoryInfo.GetFileSystemInfos())
            ...{
                if (fsi is FileInfo)
                ...{
                    length += ((FileInfo)fsi).Length;
                }
                else
                ...{
                    length += GetFilesSize(fsi.FullName);
                }
            }
            return length;
        }