using System;

using System.Linq;

using System.Collections.Generic;

​

public class Student

{

    public string FirstName

    { get; set; }

    public string LastName

    { get; set; }

    public int Age

    { get; set; }

    public Student(string firstName, string lastName, int age)

    {

        this.FirstName = firstName;

        this.LastName = lastName;

        this.Age = age;

    }

    public static void ExtractNamesBeforeSurnames(Student[] students)

    {

        var firstNameBeforeLast =

            from student in students

            where student.FirstName[0] < student.LastName[0]

            select student;

        foreach (Student student in firstNameBeforeLast)

        {

            Console.WriteLine(student.FirstName + " " + student.LastName);

        }

    }

    public static void FindStudentsInAgeGroup(Student[] students)

    {

        var between18And24 = 

            from student in students

            where (student.Age >= 18 && student.Age <= 24)

            select student;

        foreach (Student student in between18And24)

        {

            Console.WriteLine(student.FirstName + " " + student.LastName);

        }

    }

}

public class Program

{

    public static void Main()

    {

        Student[] array = new Student[] 

        {

            new Student("Mark", "Marky", 16),

            new Student("Daniel", "Wacko", 25),

            new Student("Stan", "Masterson", 24),

            new Student("Michell", "Qthilson", 18),

        };

        Student.FindStudentsInAgeGroup(array);

    }

}

​

/*Create a LINQ query that finds the first and the last name of all students,

aged between 18 and 24 years including. Use the class Student from the

previous exercise.*/