List<System.IO.FileInfo> of "*.txt" files order by descending last write time in folder "C:\\_TEST":
new System.IO.DirectoryInfo("C:\\_TEST").GetFiles("*.txt").OrderByDescending(o => o.LastWriteTime).ToList()
Latast File in folder:
new System.IO.DirectoryInfo("C:\\_TEST").GetFiles("*.txt").OrderByDescending(o => o.LastWriteTime).FirstOrDefault()