using System;
using System.Drawing;
using System.Xml.Linq;

internal class Program
{
    // This program will allow users to input their names, age and national insurance number, including
    // validation and length checks, declared variables as well as an output from the system.
    // The program will display the correct information back to the user.
    private static void Main(string[] args)
    {
        //declared variables
        string Firstname; //variable delcaring the first name
        string Surname; // variable delcaring the surname
        string NationalInsuranceNumber; //variable declaring the national insurance number
        int Age; //variable declaring the age


        //Firstname input, with presence check
        Console.WriteLine("Please enter your first name.");
        Firstname = Console.ReadLine();
        do
        {
            if (Firstname.Length == 0)
            {
                Console.WriteLine("Error! Please re enter your First name.");
                Firstname = Console.ReadLine();
            }
        }

        while (Firstname.Length == 0);
        Console.WriteLine(" ");
        Console.WriteLine("Your First Name is " + Firstname);
        Console.ReadLine();


        //Surname input, with presence check
        Console.WriteLine("Please enter your surname.");
        Surname = Console.ReadLine();
        do
        {
            if (Surname.Length == 0)
            {
                Console.WriteLine("Error! Please re enter your Surname.");
                Surname = Console.ReadLine();
            }
        }

        while (Surname.Length == 0);
        Console.WriteLine(" ");
        Console.WriteLine("Your surname is " + Surname);
        Console.ReadLine();


        //National Insurance number input, with presence check
        Console.WriteLine("Please enter your National insurance number");
        NationalInsuranceNumber = Console.ReadLine();
        do
        {
            if (NationalInsuranceNumber.Length < 13)
            {
                Console.WriteLine("Error! Please re enter your national insurance number (e.g. PE 25 34 12 B)");
                NationalInsuranceNumber = Console.ReadLine();
            }
        }

        while (NationalInsuranceNumber.Length > 13);
        {

            Console.WriteLine(" ");
            Console.WriteLine("Your national insurance number is " + NationalInsuranceNumber);
            NationalInsuranceNumber = Console.ReadLine();

        }
        //Age input, with length check
        Console.WriteLine("Please enter your age.");
        Age = Convert.ToInt32(Console.ReadLine());
        do
        {
            if (Age < 16) 
            {
                Console.WriteLine("Error! Please re enter your age (16 or above)");
            }
        }
        while (Age > 15);

        //user input display
        Console.WriteLine(" ");
        Console.WriteLine("Your Firstname is " + Firstname);
        Console.WriteLine("Your Surname is " + Surname);
        Console.WriteLine("Your National Insurance Number is " + NationalInsuranceNumber);
        Console.WriteLine("Your age is " + Age);
        Console.WriteLine("Please press enter to exit");
        Console.ReadKey();
    }
}