📁 Models/Customer.cs

using System;

namespace Hotels.Models
{
    public class Customer
    {
        public string CMTND { get; set; }
        public string Fullname { get; set; }
        public int Age { get; set; }
        public string Gender { get; set; }
        public string Address { get; set; }

        public Customer() { }

        public Customer(string cmtnd, string fullname, int age, string gender, string address)
        {
            CMTND = cmtnd;
            Fullname = fullname;
            Age = age;
            Gender = gender;
            Address = address;
        }

        public void Input()
        {
            Console.Write("Nhap CMTND: ");
            CMTND = Console.ReadLine();
            InputWithoutCMTND();
        }

        public void InputWithoutCMTND()
        {
            Console.Write("Nhap ten: ");
            Fullname = Console.ReadLine();

            Console.Write("Nhap tuoi: ");
            Age = int.Parse(Console.ReadLine());

            Console.Write("Nhap gioi tinh: ");
            Gender = Console.ReadLine();

            Console.Write("Nhap dia chi: ");
            Address = Console.ReadLine();
        }

        public void Display()
        {
            Console.WriteLine($"CMTND: {CMTND}, Ten: {Fullname}, Tuoi: {Age}, Gioi tinh: {Gender}, Dia chi: {Address}");
        }
    }
}

📁 Models/Room.cs

using System;

namespace Hotels.Models
{
    public class Room
    {
        public string RoomNo { get; set; }
        public string RoomName { get; set; }
        public float Price { get; set; }
        public int PeopleMax { get; set; }
        public int Floor { get; set; }

        public Room() { }

        public Room(string roomNo, string roomName, float price, int peopleMax, int floor)
        {
            RoomNo = roomNo;
            RoomName = roomName;
            Price = price;
            PeopleMax = peopleMax;
            Floor = floor;
        }

        public void Input()
        {
            Console.Write("Nhap ma phong: ");
            RoomNo = Console.ReadLine();

            Console.Write("Nhap ten phong: ");
            RoomName = Console.ReadLine();

            Console.Write("Nhap gia: ");
            Price = float.Parse(Console.ReadLine());

            Console.Write("Nhap so nguoi toi da: ");
            PeopleMax = int.Parse(Console.ReadLine());

            Console.Write("Nhap tang: ");
            Floor = int.Parse(Console.ReadLine());
        }

        public void Display()
        {
            Console.WriteLine($"Ma phong: {RoomNo}, Ten phong: {RoomName}, Gia: {Price}, So nguoi toi da: {PeopleMax}, Tang: {Floor}");
        }
    }
}

📁 Models/Hotel.cs

using System;
using System.Collections.Generic;

namespace Hotels.Models
{
    public class Hotel
    {
        public string HotelCode { get; set; }
        public string Name { get; set; }
        public string Address { get; set; }
        public string Type { get; set; }
        public List<Room> RoomList { get; set; }

        public Hotel()
        {
            RoomList = new List<Room>();
        }

        public void Input()
        {
            Console.Write("Nhap ma KS: ");
            HotelCode = Console.ReadLine();

            Console.Write("Nhap ten KS: ");
            Name = Console.ReadLine();

            Console.Write("Nhap dia chi: ");
            Address = Console.ReadLine();

            Console.Write("Nhap loai KS (VIP/Binh Dan): ");
            Type = Console.ReadLine();

            Console.Write("Nhap so phong cua khach san: ");
            int n = int.Parse(Console.ReadLine());
            for (int i = 0; i < n; i++)
            {
                Console.WriteLine($"\nNhap thong tin phong thu {i + 1}:");
                Room room = new Room();
                room.Input();
                RoomList.Add(room);
            }
        }

        public void Display()
        {
            Console.WriteLine($"\nMa KS: {HotelCode}, Ten KS: {Name}, Dia Chi: {Address}, Loai: {Type}");
            foreach (Room room in RoomList)
            {
                room.Display();
            }
        }
    }
}

📁 Models/Book.cs

using System;
using System.Collections.Generic;

namespace Hotels.Models
{
    public class Book
    {
        public string CMTND { get; set; }
        public string HotelCode { get; set; }
        public string RoomNo { get; set; }
        public DateTime CheckIn { get; set; }
        public DateTime CheckOut { get; set; }

        public Book() { }

        public void Input(List<Customer> customers, List<Hotel> hotels)
        {
            if (hotels.Count == 0)
            {
                Console.WriteLine("Khong co du lieu khach san!");
                return;
            }

            Console.Write("Nhap CMTND: ");
            CMTND = Console.ReadLine();
            bool exists = false;
            foreach (var c in customers)
            {
                if (c.CMTND.Equals(CMTND))
                {
                    exists = true;
                    break;
                }
            }
            if (!exists)
            {
                Console.WriteLine("Khach hang moi - nhap thong tin:");
                Customer newCus = new Customer();
                newCus.CMTND = CMTND;
                newCus.InputWithoutCMTND();
                customers.Add(newCus);
            }

            // Chon khach san
            Hotel currentHotel = null;
            do
            {
                Console.WriteLine("Danh sach khach san:");
                foreach (var h in hotels)
                    Console.WriteLine($"Ma KS: {h.HotelCode}, Ten KS: {h.Name}");
                Console.Write("Nhap ma KS: ");
                string code = Console.ReadLine();
                currentHotel = hotels.Find(h => h.HotelCode.Equals(code));
                if (currentHotel == null) Console.WriteLine("Khong tim thay ma KS. Vui long nhap lai!");
            } while (currentHotel == null);

            // Chon phong
            Room currentRoom = null;
            do
            {
                Console.WriteLine("Danh sach phong:");
                foreach (var r in currentHotel.RoomList)
                    Console.WriteLine($"Ma Phong: {r.RoomNo}, Ten Phong: {r.RoomName}");
                Console.Write("Nhap ma phong: ");
                string roomNo = Console.ReadLine();
                currentRoom = currentHotel.RoomList.Find(r => r.RoomNo.Equals(roomNo));
                if (currentRoom == null) Console.WriteLine("Khong tim thay ma phong. Vui long nhap lai!");
                else RoomNo = roomNo;
            } while (currentRoom == null);

            Console.Write("Nhap ngay CheckIn (dd/MM/yyyy): ");
            CheckIn = ConvertStringToDate(Console.ReadLine());

            Console.Write("Nhap ngay CheckOut (dd/MM/yyyy): ");
            CheckOut = ConvertStringToDate(Console.ReadLine());

            HotelCode = currentHotel.HotelCode;
        }

        private DateTime ConvertStringToDate(string value)
        {
            return DateTime.ParseExact(value, "dd/MM/yyyy", null);
        }
    }
}

📁 Program.cs

using System;
using System.Collections.Generic;
using Hotels.Models;

namespace Hotels
{
    class Program
    {
        static void Main(string[] args)
        {
            List<Customer> customers = new List<Customer>();
            List<Hotel> hotels = new List<Hotel>();
            List<Book> books = new List<Book>();

            int choose;
            do
            {
                ShowMenu();
                choose = int.Parse(Console.ReadLine());
                switch (choose)
                {
                    case 1:
                        InputHotels(hotels);
                        break;
                    case 2:
                        DisplayHotels(hotels);
                        break;
                    case 3:
                        Booking(customers, hotels, books);
                        break;
                    case 4:
                        FindAvailableRooms(hotels, books);
                        break;
                    case 5:
                        CalculateRevenue(hotels, books);
                        break;
                    case 6:
                        SearchCustomerHistory(customers, hotels, books);
                        break;
                    case 7:
                        Console.WriteLine("Thoat chuong trinh...");
                        break;
                    default:
                        Console.WriteLine("Lua chon khong hop le!");
                        break;
                }
            } while (choose != 7);
        }

        static void ShowMenu()
        {
            Console.WriteLine("\n=========== MENU ===========");
            Console.WriteLine("1. Nhap thong tin khach san");
            Console.WriteLine("2. Hien thi thong tin khach san");
            Console.WriteLine("3. Dat phong");
            Console.WriteLine("4. Tim phong con trong");
            Console.WriteLine("5. Thong ke doanh thu khach san");
            Console.WriteLine("6. Tim kiem thong tin khach hang");
            Console.WriteLine("7. Thoat");
            Console.Write("Chon chuc nang: ");
        }

        static void InputHotels(List<Hotel> hotels)
        {
            Console.Write("Nhap so luong khach san: ");
            int n = int.Parse(Console.ReadLine());
            for (int i = 0; i < n; i++)
            {
                Console.WriteLine($"\nNhap thong tin khach san thu {i + 1}:");
                Hotel h = new Hotel();
                h.Input();
                hotels.Add(h);
            }
        }

        static void DisplayHotels(List<Hotel> hotels)
        {
            if (hotels.Count == 0)
            {
                Console.WriteLine("Chua co du lieu!");
                return;
            }
            foreach (var h in hotels)
                h.Display();
        }

        static void Booking(List<Customer> customers, List<Hotel> hotels, List<Book> books)
        {
            Book book = new Book();
            book.Input(customers, hotels);
            books.Add(book);
            Console.WriteLine("Dat phong thanh cong!");
        }

        static void FindAvailableRooms(List<Hotel> hotels, List<Book> books)
        {
            if (hotels.Count == 0)
            {
                Console.WriteLine("Chua co du lieu!");
                return;
            }

            Console.Write("Nhap ma khach san: ");
            string code = Console.ReadLine();
            Hotel hotel = hotels.Find(h => h.HotelCode.Equals(code));
            if (hotel == null)
            {
                Console.WriteLine("Khong tim thay KS!");
                return;
            }

            Console.Write("Nhap ngay CheckIn (dd/MM/yyyy): ");
            DateTime checkIn = DateTime.ParseExact(Console.ReadLine(), "dd/MM/yyyy", null);

            Console.Write("Nhap ngay CheckOut (dd/MM/yyyy): ");
            DateTime checkOut = DateTime.ParseExact(Console.ReadLine(), "dd/MM/yyyy", null);

            Console.WriteLine("\nCac phong trong:");
            foreach (var room in hotel.RoomList)
            {
                bool occupied = false;
                foreach (var b in books)
                {
                    if (b.HotelCode == code && b.RoomNo == room.RoomNo)
                    {
                        if (!(checkOut <= b.CheckIn || checkIn >= b.CheckOut))
                        {
                            occupied = true;
                            break;
                        }
                    }
                }
                if (!occupied)
                    Console.WriteLine($"Ma phong: {room.RoomNo}, Ten phong: {room.RoomName}");
            }
        }

        static void CalculateRevenue(List<Hotel> hotels, List<Book> books)
        {
            foreach (var hotel in hotels)
            {
                float total = 0;
                foreach (var b in books)
                {
                    if (b.HotelCode == hotel.HotelCode)
                    {
                        Room room = hotel.RoomList.Find(r => r.RoomNo == b.RoomNo);
                        if (room != null)
                        {
                            int days = (b.CheckOut - b.CheckIn).Days;
                            total += days * room.Price;
                        }
                    }
                }
                Console.WriteLine($"Khach san {hotel.Name} thu duoc: {total} VND");
            }
        }

        static void SearchCustomerHistory(List<Customer> customers, List<Hotel> hotels, List<Book> books)
        {
            Console.Write("Nhap CMTND khach hang: ");
            string cmt = Console.ReadLine();
            Customer customer = customers.Find(c => c.CMTND.Equals(cmt));
            if (customer == null)
            {
                Console.WriteLine("Khong tim thay khach hang!");
                return;
            }

            Console.WriteLine($"Khach hang {customer.Fullname} da den cac khach san:");
            foreach (var b in books)
            {
                if (b.CMTND == cmt)
                {
                    Hotel hotel = hotels.Find(h => h.HotelCode.Equals(b.HotelCode));
                    if (hotel != null)
                        Console.WriteLine($"- {hotel.Name}");
                }
            }
        }
    }
}

✅ Tổng kết:

• Đã hoàn thiện đầy đủ 7 chức năng trong menu.

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