using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("First");

        var n = Numeros().First(a=>a==4);

        Console.WriteLine("");

        Console.WriteLine("Anyx");

        var n2 = Numeros().Any(a=>a==4);

        Console.WriteLine("");

        Console.WriteLine("Any");

        var n2b = Numeros().Any();

        Console.WriteLine("");

        Console.WriteLine("Countx");

        var n3 = Numeros().Count(a=>a==4)>0;

        Console.WriteLine("");

        Console.WriteLine("Count");

        var n3b = Numeros().Count()>0;

        Console.WriteLine("");

        Console.WriteLine("FirstList");

        var n10 = Numeros().ToList().First(a=>a==4);

        Console.WriteLine("");

        Console.WriteLine("AnyList");

        var n20 = Numeros().ToList().Any(a=>a==4);

        Console.WriteLine("");

        Console.WriteLine("sIEnumerable");

        var n4 = MaFonctionIndex(Numeros(),4);

        Console.WriteLine(n4);

        Console.WriteLine("");

        Console.WriteLine("sList");

        var n5 = MaFonctionIndexList(Numeros().ToList(),4);

        Console.WriteLine(n5);

        Console.WriteLine("");

    }

    public static IEnumerable<int> Numeros()

    {

        foreach(var i in Enumerable.Range(1,10) )

        {

            Console.WriteLine("Iteration:"+i);

            yield return i;

        }

    }

    public static int MaFonctionIndex(IEnumerable<int>coll,int val)

    {

        return coll.Where(a=>a==val).FirstOrDefault();

    }

    public static int MaFonctionIndexList(List<int>coll,int val)

    {

        return coll.Where(a=>a==val).FirstOrDefault();

    }

​

}