int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54, 
                    83, 23, 87, 435, 67, 12, 19 };

int first = numbers.AsQueryable().First();

Console.WriteLine(first);

int[] numbers = { 9, 34, 65, 92, 87, 435, 3, 54, 
                  83, 23, 87, 435, 67, 12, 19 };

// Get the first number in the array that is greater than 80.
int first = numbers.AsQueryable().First(number => number > 80);

Console.WriteLine(first);

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

public class MainClass{
   public static void Main(){
       int[] numbers = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
       var query = numbers.First();
       Console.WriteLine("The first element in the sequence");
       Console.Write(query);
       query = numbers.Last();
       Console.WriteLine("The last element in the sequence");
       Console.Write(query);
       Console.WriteLine("The first even element in the sequence");
       query = numbers.First(n => n % 2 == 0);
       Console.Write(query);
       Console.WriteLine("The last even element in the sequence");
       query = numbers.Last(n => n % 2 == 0);
       Console.Write(query);
   }
}

//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() {
        string[] presidents = {"G", "H", "a", "H", "over", "Jack"};

        string name = presidents.First(p => p.StartsWith("H"));
        Console.WriteLine(name);
    }
}