一个library,相当于一个rootfolder

picLib.RootFolder.SubFolders
操作library的方式：
                        SPList oList = web.Lists[ListNames.AboutNRC];
                        SPDocumentLibrary picLib = (SPDocumentLibrary)oList;

                        foreach (SPFolder item in picLib.RootFolder.SubFolders)
                        {
                            if (item.Name == "Company Album")
                            {
                                LiteralImage.Text = loadAboutImg(item);
                            }
                            else
                            {
                                continue;
                            }
                        }