using System;

using System.Linq;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        DateOnly birthDate = DateOnly.MinValue;

        while (birthDate == DateOnly.MinValue)

        {

            Console.Write("Enter your birth date(yyyy-MM-dd)");

            if (!DateOnly.TryParse(Console.ReadLine(), out birthDate))

            {

                Console.WriteLine("Invalid date");

            }

        }

        Console.WriteLine($"You were born on {birthDate:dddd dd MMMM yyyy}\n");

        Console.WriteLine($"Your birthday will be {birthDate:dddd} too in the following years:");

​

        Enumerable.Range(birthDate.Year + 1, 100)

            .Select(y=> new DateOnly(y,birthDate.Month,birthDate.Day))

            .Where(d=>d.DayOfWeek == birthDate.DayOfWeek)

            .ForEach(d=>

            {

                Console.WriteLine($"\t{d.Year} ({d.Year - birthDate.Year, 2:G} years old)");

            });

    }

}

​

public static class EnumerableExtension

{

    public static void ForEach<T>(this IEnumerable<T> enumeration, Action<T> action)

    {

        foreach(T item in enumeration)

            {

                action(item);

            }

    }

}