获取文件下下的所有文件

static void CollectFiles(DirectoryInfo dir)
        {
            if (ExcludeFolders.Contains(dir.Name))
            {
                return;
            }
            FileSystemInfo[] SystemFiles = dir.GetFileSystemInfos();
            if (SystemFiles.Length == 0)
            {
                return;
            }
            else
            {
                foreach (var file in dir.GetFiles("*.bak"))
                {
                    FileList.Add(file);
                }
                foreach (var folder in dir.GetDirectories())
                {
                    CollectFiles(folder);
                }
            }

        }