using System;

using System.Collections.Generic;

using System.Linq;

​

public class Student

{

    public int StudentID

    {

        get;

        set;

    }

​

    public string StudentName

    {

        get;

        set;

    }

​

    public int Age

    {

        get;

        set;

    }

}

​

public class Program

{

    public static void Main()

    {

        IList<Student> studentList = new List<Student>()

        {

        new Student()

        {

        StudentID = 1, StudentName = "John", Age = 18

        }

​

        , new Student()

        {

        StudentID = 2, StudentName = "Steve", Age = 15

        }

​

        , new Student()

        {

        StudentID = 3, StudentName = "Bill", Age = 25

        }

​

        , new Student()

        {

        StudentID = 4, StudentName = "Ram", Age = 20

        }

​

        , new Student()

        {

        StudentID = 5, StudentName = "Ron", Age = 19

        }

        }

​

        ;

        // checks whether all the students are teenagers    

        bool areAllStudentsTeenAger = studentList.All(s => s.Age > 12 && s.Age < 20);

        Console.WriteLine(areAllStudentsTeenAger);

        areAllStudentsTeenAger = studentList.Any(s => s.Age > 12 && s.Age < 20);

        Console.WriteLine(areAllStudentsTeenAger);

        areAllStudentsTeenAger = studentList.Contains(new Student(){StudentID  = 3, StudentName = "Bill",  Age = 25});

        Console.WriteLine(areAllStudentsTeenAger);

        areAllStudentsTeenAger = studentList.Contains(new Student(){StudentID  = 3, StudentName = "Bill"}, new StudentComparer());

        Console.WriteLine(areAllStudentsTeenAger);

    }

    class StudentComparer: IEqualityComparer<Student>{

        public bool Equals(Student x, Student y){

            return x.StudentID == y.StudentID && x.StudentName.Equals(y.StudentName, StringComparison.OrdinalIgnoreCase);

        }

        public int GetHashCode(Student obj){

            return obj.GetHashCode();

        }

    }

}