Linq E

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;

namespace Linq_Set_op_element_op
{
  class stringComparer : IEqualityComparer<string>
  {
    public bool Equals(string s1, string s2)
    {
      return string.Compare(s1 , s2)==0;
    }

    public int GetHashCode(string obj)
    {
      return obj.GetHashCode();
    }
  }

  class Program
  {
    static void stampa(IEnumerable<string> elenco)
    {
      foreach (string s in elenco) Console.WriteLine(s);
    }


    static void Main(string[] args)
    {
      string[] files1 = Directory.GetFiles(@"g:\tempSuG")
                        .Select(path_e_nome => Path.GetFileName(path_e_nome)).ToArray();
      string[] files2 = Directory.GetFiles(@"g:\PresenzeFAD\3B")
                        .Select(path_e_nome => Path.GetFileName(path_e_nome)).ToArray();

      var concatenamento = files1.Concat(files1);
      var unione = files1.Union(files2);


      unione = files1.Union(files2);
      //Console.WriteLine( $"{files1.Count()} {files2.Count()}  {unione.Count()}");

      var intersezione = files1.Intersect(files2);
      //stampa(intersezione);

      var differenza = files2.Except(files1);
      //stampa(differenza);

      Console.WriteLine(unione.First());
      Console.WriteLine(unione.First(nomeFile => nomeFile.Length>10));

      Console.WriteLine(unione.Last());
      Console.WriteLine(unione.ElementAt(12));
      Console.WriteLine(unione.Min());
      Console.WriteLine(unione.Min(nomeFile => nomeFile.Length));
      Console.WriteLine(unione.Sum(nomeFile => nomeFile.Length));
      Console.WriteLine(unione.Average(nomeFile => nomeFile.Length));
      Console.WriteLine(unione.Any(nomeFile => nomeFile.Length>30));
      Console.WriteLine(unione.All(nomeFile => nomeFile.Length>30));

    }
  }
}