First

In this chapter you will learn:

How to use First operator
Use First with expression
First with string method
Retrieving all strings in an array whose length matches that of the shortest string

Get to know First operator

using System;//from  java2s. c  om
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main()
    {
        int[] numbers = { 1, 2, 3, 4, 5 };
        int first = numbers.First();
        int firstEven = numbers.First(n => n % 2 == 0);
        Console.WriteLine(first);
        Console.WriteLine(firstEven);
    }
}

The output:

Use First with expression

using System;/* j ava  2  s . c om*/
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(n => n % 2 == 0);
       Console.Write(query);
   }
}

First with string method

using System;/*from j a  va2s.c o  m*/
using System.Linq;
using System.Collections;
using System.Collections.Generic;

public class MainClass {
    public static void Main() {
        string[] presidents = {"G", "java2s.com", "a", "H", "over", "Jack"};

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

First after select

using System;//  ja v a 2 s . c om
using System.Collections.Generic;
using System.Linq;
public class MainClass {
    public static void Main() {

        string[] names = { "Java", "java2s.com", "java2", "java2s" };

        IEnumerable<string> outerQuery = names
          .Where(n => n.Length == names.OrderBy(n2 => n2.Length)
                                        .Select(n2 => n2.Length).First());
    }
}

Next chapter...

What you will learn in the next chapter: