Drop Down List Value not passing to controller - asp.net-mvc-4

Question

This question should be very simple.. I am trying to pass values in my drop down list in my view to the controller.. I'm not getting errors but it's sending a null value for that property. Please help..
My code is as follows:
Controller:
public ActionResult Create()
{
var list = new []
{
new Room{ RoomID = 1, Building = "FAYARD HALL"},
new Room{ RoomID = 2, Building = "WHATEVER HALL"},
new Room{ RoomID = 3, Building = "TIME SQUARE"},
new Room{ RoomID = 4, Building = "MISSISSIPPI"},
new Room{ RoomID = 5, Building = "NEW YORK"},
};
var selectList = new SelectList(list,"RoomID", "Building");
ViewData["BuildingList"] = selectList;
return View();
}
//
// POST: /Room/Create
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(Room room)
{
if (ModelState.IsValid)
{
db.Rooms.Add(room);
db.SaveChanges();
return RedirectToAction("Index");
}
return View(room);
}
MY VIEW:
<div>
#Html.LabelFor(model => model.Building, "Building")
</div>
<div>
#Html.DropDownList("BuildingList", String.Empty)
#Html.ValidationMessageFor(model => model.Building)
</div>
Please help...
Thank you.

Answer 1

Is your drop down populated? Given your code I think you need the following to do so:
#Html.DropDownListFor(model => model.Building, ViewData["BuildingList"])
ie. bind the selected value to the Building property of your Room and use the drop down list from your view model to populate the list.
I'm also not sure this is what your intention is. It seems a bit fishy that you are populating a drop down list with rooms and then based on the selection you are creating a new room.
Edit
Ok I'm going to make things a lot easier for you.
I'll start with your classes. Here is the room I am assuming you're working with:
public class Room
{
public int RoomId { get; set; }
public string Building { get; set; }
}
Now let's do something a bit better than using ViewData. I've created a view model for you. You will populate this with your select list and the item you choose in the view will be bound into the SelectedRoomId when you post the form.
public class ViewModel
{
public int SelectedRoomId { get; set; }
public SelectList RoomOptions { get; set; }
}
Controller
private SelectList GetSelectList()
{
var list = new[]
{
new Room { RoomId = 1, Building = "FAYARD HALL"},
new Room { RoomId = 2, Building = "WHATEVER HALL"},
new Room { RoomId = 3, Building = "TIME SQUARE"},
new Room { RoomId = 4, Building = "MISSISSIPPI"},
new Room { RoomId = 5, Building = "NEW YORK"}
};
return new SelectList(list, "RoomId", "Building");
}
public ActionResult Create()
{
ViewModel viewModel = new ViewModel
{
RoomOptions = GetSelectList()
};
return View(viewModel);
}
[HttpPost]
public ActionResult Create(ViewModel viewModel)
{
if (ModelState.IsValid)
{
// Save here
// create a new room using the SelectedOptionId in the viewModel
return RedirectToAction("Index", "Home");
}
// repopulate the list if something failed
viewModel.RoomOptions = GetSelectList();
return View(viewModel);
}
View
#model PathToYourViewModel.ViewModel
#using (Html.BeginForm())
{
#Html.DropDownListFor(model => model.SelectedRoomId, Model.RoomOptions, "-- select an option --")
<button type="submit">Submit</button>
};
Tried and tested. Good luck!

Answer 2

The model binding takes place with help of the names property in mvc .
In your case the name of your control is BuildingList:
#Html.DropDownList("BuildingList", (SelectList)ViewData["BuildingList"])
Therefore at your controller Action will go as follows:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Create(FormCollection collection)
{
var selectedValue = collection["BuildingList"];
}