How to recursively list all the files in a directory in C#?

Question

How to recursively list all the files in a directory and child directories in C#?

Answer 1

IEnumerable GetFilesFromDir(string dir) =>
 Directory.EnumerateFiles(dir).Concat(
 Directory.EnumerateDirectories(dir)
          .SelectMany(subdir => GetFilesFromDir(subdir)));