Program.cs

using System;
using System.Collections.Generic;

namespace AlgorithmsRetakeExam
{
    class Program
    {
        static Hotel hotel = new Hotel("Hotel1");

        static void Main(string[] args)
        {
            string line;

            while ("END" != (line = Console.ReadLine()))
            {
                string[] cmdArgs = line.Split(' ');

                switch (cmdArgs[0])
                {
                    case "Add":
                        AddDog(cmdArgs[1], int.Parse(cmdArgs[2]));
                        break;
                    case "AverageAge":
                        AverageAge();
                        break;
                    case "FilterDogs":
                        FilterDogsByAge(int.Parse(cmdArgs[1]));
                        break;
                    case "SortByName":
                        SortAscendingByName();
                        break;
                    case "SortByAge":
                        SortDescendingByAge();
                        break;
                    case "CheckDog":
                        CheckDogIsInHotel(cmdArgs[1]);
                        break;
                    case "Print":
                        ProvideInformationAboutAllDogs();
                        break;
                }
            }
        }

        private static void ProvideInformationAboutAllDogs()
        {
            string[] info = hotel.ProvideInformationAboutAllDogs();
            foreach (string item in info)
            {
                Console.WriteLine(item);
            }
        }

        private static void CheckDogIsInHotel(string name)
        {
            if (hotel.CheckDogIsInHotel(name))
            {
                Console.WriteLine($"Dog {name} is in the hotel.");
            }
            else
            {
                Console.WriteLine($"Dog {name} is not in the hotel.");
            }
        }
        private static void SortDescendingByAge()
        {
            hotel.SortDescendingByAge();
            Console.WriteLine("The youngest dog is: " + hotel.Dogs[hotel.Dogs.Count - 1].Name);
        }
        private static void SortAscendingByName()
        {
            hotel.SortAscendingByName();
            Console.WriteLine("First dog is: " + hotel.Dogs[0].Name);
        }
        private static void FilterDogsByAge(int age)
        {
            List<string> dogs = hotel.FilterDogsByAge(age);
            Console.WriteLine("Filtered dogs: " + string.Join(", ", dogs));
        }

        private static void AverageAge()
        {
            double averageAge = hotel.AverageAge();
            Console.WriteLine($"Average age: {averageAge:F2}");
        }

        private static void AddDog(string name, int age)
        {
            hotel.AddDog(name, age);
            Console.WriteLine($"Added dog {name}.");
        }
    }
}