使用c＃检索父/子查询结果SQL Server

Question

what I am doing here now is the probably the worst way of fulfilling my requirements but I haven't found any other way.

here is my sample database structure;

Here is the script that I use in order to retrieve the certain values;

SELECT DISTINCT h.HotelID, h.HotelName, r.RoomCode, r.RoomName, r.RoomID 
FROM RoomsInHotel rh 
INNER JOIN Hotels h ON rh.HotelID = h.HotelID 
INNER JOIN  Rooms r ON rh.RoomID = r.RoomID 
order by h.HotelName, r.RoomCode;

Here is the result that the above script is giving me back;

everything is fine till here.

I need to move to C# code from here. What I would like to achieve is the following result;

Here is where I am worried about. I use Linq to achieve this thing and the below code is the code that I used for the above console result.

    public class Hotel { 
      public int HotelID {get; set; }
      public string HotelName {get; set; }
      public IQueryable<Room> Rooms {get; set; }
    }

    public class HotelWithOneRoom {
        public int HotelID { get; set; }
        public string HotelName { get; set; }
        public Room Room { get; set; }
    }

    public class Room { 
      public int RoomID {get; set; }
      public string RoomCode {get; set; }
      public string RoomName { get; set; }
    }

    class Program {

        static void Main(string[] args) {

            #region _assets

            IList<HotelWithOneRoom> tempHotelWithOneRoom = new List<HotelWithOneRoom>();
            IList<Hotel> tempDistinctHotels = new List<Hotel>();
            IList<Room> tempRooms = new List<Room>();

            #endregion

            #region _connectionString

            var connectionString = "Data Source=TOSHIBA-PC\\SQLEXPRESS;Initial Catalog=tbAccomm;Integrated Security=True";

            #endregion

            using (SqlConnection conn = new SqlConnection(connectionString)) {

                using(SqlCommand cmd = conn.CreateCommand()) {

                    #region _connect to db, generate script and retrieve values

                    cmd.CommandText = "SELECT DISTINCT h.HotelID, h.HotelName, r.RoomCode, r.RoomName, r.RoomID FROM RoomsInHotel rh INNER JOIN Hotels h ON rh.HotelID = h.HotelID INNER JOIN Rooms r ON rh.RoomID = r.RoomID order by h.HotelName, r.RoomCode;";
                    cmd.CommandType = System.Data.CommandType.Text;

                    conn.Open();
                    SqlDataReader r = cmd.ExecuteReader();

                    #endregion

                    #region _assigning the values to tempHotelWithOneRoom

                    while (r.Read()) {

                        tempHotelWithOneRoom.Add(new HotelWithOneRoom {
                            HotelID = int.Parse(r["HotelID"].ToString()),
                            HotelName = r["HotelName"].ToString(),
                            Room = new Room {
                                RoomID = int.Parse(r["RoomID"].ToString()),
                                RoomCode = r["RoomCode"].ToString(),
                                RoomName = r["RoomName"].ToString()
                            }
                        });
                    }

                    #endregion

                    foreach (var item in tempHotelWithOneRoom) {

                        if (tempDistinctHotels.Where(x => x.HotelID == item.HotelID).Count() < 1) {

                            tempDistinctHotels.Add(new Hotel { 
                                HotelID = item.HotelID,
                                HotelName = item.HotelName
                            });

                            var _tempHotel = tempDistinctHotels.Single(x => x.HotelID == item.HotelID);
                            var _tempRoomList = new List<Room>();

                            if (_tempHotel.Rooms != null) { 
                                foreach (var _item in _tempHotel.Rooms) {
                                    _tempRoomList.Add(_item);
                                }
                            }

                            _tempRoomList.Add( new Room { 
                                RoomCode = item.Room.RoomCode,
                                RoomID = item.Room.RoomID,
                                RoomName = item.Room.RoomName
                            });

                            _tempHotel.Rooms = _tempRoomList.AsQueryable();

                        } else {

                            var _tempHotel = tempDistinctHotels.Single(x => x.HotelID == item.HotelID);
                            var _tempRoomList = new List<Room>();

                            if (_tempHotel.Rooms != null) { 
                                foreach (var _item in _tempHotel.Rooms) {
                                    _tempRoomList.Add(_item);
                                }
                            }

                            _tempRoomList.Add( new Room { 
                                RoomCode = item.Room.RoomCode,
                                RoomID = item.Room.RoomID,
                                RoomName = item.Room.RoomName
                            });

                            _tempHotel.Rooms = _tempRoomList.AsQueryable();
                        }
                    }

                    #region _output the result

                    foreach (var item in tempDistinctHotels) {

                        Console.WriteLine(
                            "Hotel Name : " + item.HotelName + ", " +  "Room Count : " + item.Rooms.Count()
                            );

                        foreach (var item2 in item.Rooms) {
                            Console.WriteLine("--" + item2.RoomCode + ", " + item2.RoomName);
                        }
                    }

                    #endregion

                    r.Close();
                    Console.Read();
                }

            }

        }
    }

IMO, if there was a competition on the worst c# code, I would be winning that competition with this code. (Would I?)

So, what is the most optimized way of doing what I do?

Answer 1

C# is not my language of choice but here you go:

Dictionary<int, Hotel> Hotels = new Dictionary<int, Hotel> ();
while (r.Read()) {
    if (!Hotels.ContainsKey(r["HotelID"])) {
        NewHotel Hotel= new Hotel();
        NewHotel.HotelID = r["HotelID"];
        Newhotel.HotelName = r["HotelName"];
        NewHotel.Rooms = new Dictionary<int, Room> ();
        Hotels.Add(NewHotel);
    }
    Room NewRoom = new Room();
    NewRoom.RoomID = r["RoomName"];
    NewRoom.RoomCode = r["RoomCode"];
    NewRoom.RoomName = r["RoomName"];
    Hotels.Items("HotelID").Rooms.Add(NewRoom);
}

Like jpmcclung pointed out, you'll need some Software engineering Skills to create successful Applications. The bigger your Project, the more design and planning is called for.

Answer 2

The best way to get around writing code like this is to study up on the practice of test driven design. This code is screaming for it. To see it in action I would check out Brad Wilson's new TDD Full Throttle video at TekPub (http://shop.tekpub.com/products/ft_tdd_wilson) it is 12 bucks but it will be worth it. Otherwise there are numerous resourses on the subject.

Specifically, why do you need a HotelWithOneRoom? Just add one room to the Rooms list in a regular hotel. Why don't you override .ToString() on the Hotel and use the StringBuilder to create the output line for a hotel? Those are just a few things off the top of my head but if you use TDD it will help organize your design practice and get some of this code out of your way.

Answer 3

Since you include IQueryable in your example, can we assume that LINQ to SQL or EF is an option for your solution? If so, realize that they support projecting into object heirarchies directly.

Asssuming you have associations set between your tables, it could be as simple as:

var query = from hotel in context.hotels
             select new Hotel { HotelID = hotel.HotelID,
                                HotelName = hotel.HotelName,
                                Rooms = (from room in hotel.Rooms
                                        select new Room { 
                                            RoomID = room.RoomID,
                                            RoomCode = room.RoomCode, 
                                            RoomName = room.RoomName })
                                        .Distinct()
             }; 

Answer 4

I think you could start from the beginning here and avoid some confusion by renaming your Tables. I think your table names should be Hotel, Room and RoomType (I'm not a fan of pluralized table names, but that's beside the point).

To think in 'Domain' terms, you have a Hotel. A hotel has Rooms. Each room is defined as a type of room, Double, Single, etc...

Anyway, I threw some code together that's doing the same thing yours is doing. It's a little clearer I think. For database access, I used Massive https://github.com/robconery/massive because it's quick and fun.

Anyway, here is the code I came up with.

    class Program {
        static void Main(string[] args) {
            const string sqlStmnt = @"SELECT h.HotelID, h.HotelName, r.HotelRoomID, rt.RoomTypeCode, rt.RoomTypeName FROM Hotel h INNER JOIN HotelRoom r ON r.HotelID = h.HotelID INNER JOIN  RoomType rt ON r.RoomTypeID = rt.RoomTypeID order by h.HotelName, rt.RoomTypeCode";
            var context = new HotelContext();
            var hotelData =  context.Query(sqlStmnt);
            var hotelList = new List<Hotel>();

            //Load our objects
            foreach (dynamic data in hotelData) {
                int hotelID = data.HotelID;
                var hotel = hotelList.Where(h => h.HotelID == hotelID).FirstOrDefault()
                                      ?? new Hotel() {HotelName = data.HotelName};
                hotel.AddRoom(new HotelRoom { HotelRoomID = data.HotelRoomID, RoomType = new RoomType{ TypeCode = data.RoomTypeCode, TypeDescription = data.RoomTypeName}});

                if (hotel.HotelID != 0) {continue;}
                hotel.HotelID = hotelID;
                hotelList.Add(hotel);
            }

            //Display our output
            foreach (var hotel in hotelList) {
                Console.WriteLine("Hotel Name : " + hotel.HotelName + ", Room Count : " + hotel.HotelRooms.Count());
                foreach (var room in hotel.HotelRooms) {
                    Console.WriteLine("--" + room.RoomType.TypeCode + ", " + room.RoomType.TypeDescription);
                }
            }

            Console.ReadLine();
         }
    }

Here is my Database stuff.

    public class HotelContext : DynamicModel {
        public HotelContext():base("test") {
        PrimaryKeyField = "HotelID";
        TableName = "Hotel";
        }
    }

Here are the classes I used. Couldn't ever figure out what your HotelWithOneRoom was meant for.

    public class Hotel{
        private readonly List<HotelRoom> _rooms = new List<HotelRoom>();
        public int HotelID { get; set; }
        public string HotelName { get; set; }
        public void AddRoom(HotelRoom room) {_rooms.Add(room);}
        public IQueryable<HotelRoom> HotelRooms {get {return _rooms.AsQueryable();}}
    }
    public class HotelRoom {
        public int HotelRoomID { get; set; }
        public RoomType RoomType { get; set; }
    }

    public class RoomType {
        public string TypeCode { get; set; }
        public string TypeDescription { get; set; }
    }