using System;

using System.Collections.Generic;

public class Program

{

    static List<Student> Record = new List<Student>();

    public static void Main()

    {

        bool run = true;

        while(run){

            Console.WriteLine("1. Enter Student Info\n2. View\n3. Search\n4. Exit");

            int ans = int.Parse(Console.ReadLine());

            switch (ans){

                case 1:

                    addStudent();

                    break;

                case 2:

                    Console.WriteLine("\nView Student Info by: \n1. ID\n2. Last Name\n3. Age");

                    int i = int.Parse(Console.ReadLine());

                    switch (i){

                        case 1:

                            ViewID();

                            break;

                        case 2:

                            ViewLN();

                            break;

                        case 3:

                            ViewAge();

                            break;

                        default:

                            Console.WriteLine("Invalid Input");

                            break;

                    }

                    break;

                case 3:

                    search();

                    break;

                case 4:

                    Console.WriteLine("Exiting program..");

                    run = false;

                    break;

                default:

                    Console.WriteLine("Invalid Input\n");

                    break;

            }

            Console.WriteLine("");

        }

    }

    public static void addStudent(){

        Console.WriteLine("Enter Student ID: ");

        int id = int.Parse((Console.ReadLine()));

        Console.WriteLine("Enter Last Name: ");

        string lName = Console.ReadLine();

        Console.WriteLine("Enter First Name: ");

        string fName = Console.ReadLine();

        Console.WriteLine("Enter Age: ");

        int age = int.Parse((Console.ReadLine()));

        Student stu = new Student(id,lName,fName,age);

        Record.Add(stu);

        Console.WriteLine("\nStudent has been added.");

    }

    static void ViewID(){

        List<Student> byID = new List<Student>(Record);

        byID.Sort((s1,s2) => s1.Id.CompareTo(s2.Id));

        var a1 = "Last Name".PadRight(10);

        var a2 = "First Name".PadRight(10);

        Console.WriteLine("ID\t{0}\t{1}\tAge",a1,a2);

        foreach(var x in byID){

            display(x);

        }

    }

    public static void ViewLN(){

        List<Student> byLN = new List<Student>(Record);

        byLN.Sort((s1,s2) => s1.LastName.CompareTo(s2.LastName));

        Console.WriteLine("ID\tLast Name\tFirst Name\tAge");

        foreach(var x in byLN){

            display(x);

        }

    }

    public static void ViewAge(){

        List<Student> byAge = new List<Student>(Record);

        byAge.Sort((s1,s2) => s1.LastName.CompareTo(s2.Age));

        Console.WriteLine("ID\tLast Name\tFirst Name\tAge");

        foreach(var x in byAge){

            display(x);

        }

    }

    public static void search(){

        Console.WriteLine("Search Records by:\n1. Last Name\n2. ID");

        int i = int.Parse(Console.ReadLine());

        switch (i){

            case 1:

            Console.WriteLine("Enter Last Name: ");

            string input = Console.ReadLine();

            List<Student> LN = Record.FindAll(s => s.LastName.Equals(input));

            if (LN.Count > 0){

                Console.WriteLine("Student records found:");

                foreach (var x in LN){

                    display(x); 

                }

            }

            else{

                Console.WriteLine("Student records not found.");

            }

            break;

        case 2:

            Console.WriteLine("Enter Student ID:");

            int stuID = int.Parse(Console.ReadLine());

            Student stuId = Record.Find(s => s.Id == stuID);

            if (stuId != null) {

                Console.WriteLine("Student record found:");

                Console.WriteLine("ID\tLast Name\tFirst Name\tAge");

                    display(stuId);

            }

            else {

                Console.WriteLine("Student record not found."); 

            }

            break;

        default:

            Console.WriteLine("Invalid Input");

            break;

        }

    }

    static void display(Student stu){

        Console.WriteLine("{0}\t{1}\t{2}\t{3}",stu.Id,stu.LastName.PadRight(10),stu.FirstName.PadRight(10),stu.Age);

    }

}

class Student {

    public int Id { get; set; }

    public string LastName { get; set; }

    public string FirstName { get; set; }

    public int Age { get; set; }

​

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

    {

        Id = id;

        LastName = lastName;

        FirstName = firstName;

        Age = age;

    }

}