using System.Collections.Generic;
public static void Main()
var foos = new List<Foo>()
var actives = foos.Where(x => x.IsActive=true).ToList();
Console.WriteLine(actives.Count);
var ages = foos.Where(x => x.Age = 1).ToList();
public Foo(bool active, int age)
public bool IsActive { get; set; }
public int Age { get; set; }