public static bool AreFileContentsEqual(String path1, String path2) =>
File.ReadAllBytes(path1).SequenceEqual(File.ReadAllBytes(path2));
public static bool AreFileContentsEqual(FileInfo fi1, FileInfo fi2) =>
fi1.Length == fi2.Length &&
(fi1.Length == 0 || File.ReadAllBytes(fi1.FullName).SequenceEqual(
File.ReadAllBytes(fi2.FullName)));