string[] fruits = { "apple", "banana", "mango", 
                      "orange", "passionfruit", "grape" };

long count = fruits.AsQueryable().LongCount();

Console.WriteLine("There are {0} fruits in the collection.", count);

class Pet
{
    public string Name { get; set; }
    public int Age { get; set; }
}

public static void LongCountEx2()
{
    Pet[] pets = { new Pet { Name="Barley", Age=8 },
                   new Pet { Name="Boots", Age=4 },
                   new Pet { Name="Whiskers", Age=1 } };

    const int Age = 3;

    // Count the number of Pet objects where Pet.Age is greater than 3.
    long count = pets.AsQueryable().LongCount(pet => pet.Age > Age);

    Console.WriteLine("There are {0} animals over age {1}.", count, Age);
}

//引入命名空间
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class MainClass {
    public static void Main() {
        long count = Enumerable.Range(0, int.MaxValue).Concat(Enumerable.Range(0, int.MaxValue)).LongCount();
        Console.WriteLine(count);
    }
}

//引入命名空间
using System;
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class MainClass {
    public static void Main() {
        long count = Enumerable.Range(0, int.MaxValue).
        Concat(Enumerable.Range(0, int.MaxValue)).LongCount(n => n > 1 && n < 4);
        Console.WriteLine(count);
    }
}