Why are my cascading dropdown lists not working? (ASP.NET [MVC 3])

I'm having problem with my cascading dropdownlist (DDL), it perfectly works fine when you choose the first DDL and when you select the second DDL the third DLL do not fire and the value is null.

Here's my JS

$('#Building_SelectedBuildingID').change(function () {
        var SelectedBuildingID = $(this).val();
        $.getJSON('@Url.Action("ActionFloor")', { buildingId: SelectedBuildingID }, function (oFloors) {
            var SelectFloorID = $('#Floor_SelectedItem');
            SelectFloorID.empty();
            $.each(oFloors, function (index, Floor) {
                SelectFloorID.append(
                    $('<option/>')
                        .attr('value', Floor.Code)
                        .text(Floor.Description)
                );
            });
        });
    });

    $('#Floor_SelectedFloorID').change(function () {
        var SelectedBuildingID = $('#Building_SelectedBuildingID').val();
        var selectedFloorId = $(this).val();
        $.getJSON('@Url.Action("ActionLocation")', { buildingId: SelectedBuildingID,floorId: selectedFloorId }, function (oLocations) {
            var SelectLocationID = $('#Location_SelectedItem');
            SelectLocationID.empty();

            $.each(oLocations, function (index, Location) {
                SelectLocationID.append(
                    $('<option/>')
                        .attr('value', Location.Code)
                        .text(Location.Description)
                );
            });
        });
    });
});

View

@model FA_CS.Models.Operation.NewRegistration  
<table style="width:100%;">
    <tr>
        <td colspan="2">
            <strong>Location</strong></td>
    </tr>
    <tr>
        <td class="style1">
            @Html.LabelFor(m => m.Building)</td>
        <td>
            @Html.DropDownListFor(x => x.Building.SelectedBuildingID, new SelectList(Model.Building.BuildingItems, "code", "description"))
            </td>
    </tr>
    <tr>
        <td class="style1">
            @Html.LabelFor(m => m.Floor) </td>
        <td> 
            @Html.DropDownListFor(x => x.Floor.SelectedItem, Enumerable.Empty<SelectListItem>())
                </td> 
    </tr>
    <tr>
        <td class="style1">
            @Html.LabelFor(m => m.Location)</td>
        <td>
            @Html.DropDownListFor(x => x.Location.SelectedItem, Enumerable.Empty<SelectListItem>())
            </td>
    </tr>
</table>

Model

Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.ComponentModel.DataAnnotations
Imports System.Globalization
Public Class ItemClass
    Private _code As String
    Private _description As String
    Private _ClassItems As System.Collections.Generic.List(Of ItemClass)
    Private _Type As MDL.Type
    Private _Types As System.Collections.Generic.List(Of MDL.Type)
    Private _SelectedClassItem As String
    Private _SelectedTypeItem As String
    Private _SelectedSubTypeItem As String



    Public Property SelectedClassID As String
        Get
            Return _SelectedClassItem
        End Get
        Set(value As String)
            _SelectedClassItem = value
        End Set
    End Property

    Public Property SelectedTypeID As String
        Get
            Return _SelectedTypeItem
        End Get
        Set(value As String)
            _SelectedTypeItem = value
        End Set
    End Property

    Public Property SelectedSubTypeID As String
        Get
            Return _SelectedSubTypeItem
        End Get
        Set(value As String)
            _SelectedSubTypeItem = value
        End Set
    End Property

    <DataType(DataType.Text)> _
    <Display(Name:="Type")> _
    Public Property code() As String
        Get
            Return _code
        End Get
        Set(ByVal Value As String)
            _code = Value
        End Set
    End Property
    <DataType(DataType.Text)> _
    <Display(Name:="Type")> _
    Public Property description() As String
        Get
            Return _description
        End Get
        Set(ByVal Value As String)
            _description = Value
        End Set
    End Property

    Public Property ClassItems() As System.Collections.Generic.List(Of ItemClass)
        Get
            Return _ClassItems
        End Get
        Set(ByVal value As System.Collections.Generic.List(Of MDL.ItemClass))
            _ClassItems = value
        End Set
    End Property
    ''' <summary>
    ''' Property for collection of Type
    ''' </summary>
    ''' <pdGenerated>Default opposite class collection property</pdGenerated>
    Public Property Type() As MDL.Type
        Get
            Return _Type
        End Get
        Set(ByVal value As MDL.Type)
            _Type = value
        End Set
    End Property
    Public Property Types() As System.Collections.Generic.List(Of Type)
        Get
            Return _Types
        End Get
        Set(ByVal value As System.Collections.Generic.List(Of Type))
            _Types = value
        End Set
    End Property
    Public Overrides Function ToString() As String
        Return Me._description
    End Function


End Class

Controller

  public JsonResult GetCascadeBuildings()
    {
        return Json(FA_CS.Helpers.BuildingList.Status, JsonRequestBehavior.AllowGet);
    }

    public JsonResult GetCascadeFloors(string buildingCode)
    {
        var gathererS = new List<MDL.Floor>();
        gathererS = GetFloors(buildingCode);
        return Json(gathererS, JsonRequestBehavior.AllowGet);
    }

    public List<MDL.Floor> GetFloors(string BuildingCode)
    {
        FAWebService.Service1 faws = new FAWebService.Service1();
        Array arr = faws.GatherFloor(BuildingCode);
        MDL.Floor oFloor = new MDL.Floor();
        List<MDL.Floor> oFloors = new List<MDL.Floor>();
        foreach (FAWebService.Floor itm in arr)
        {
            oFloors.Add(new MDL.Floor { SelectedItem = itm.Code, Description = itm.Description });
        }
        return oFloors;

    }


    public JsonResult GetCascadeLocations(string buildingCode, string floorCode)
    {
        var gatherer = new MDL.Location();
        var gathererS = new List<MDL.Location>();
        gathererS = GetLocations(buildingCode, floorCode);
        return Json(gathererS, JsonRequestBehavior.AllowGet);
    }

    public List<MDL.Location> GetLocations(string BuildingCode, string floorCode)
    {
        FAWebService.Service1 faws = new FAWebService.Service1();
        Array arr = faws.GatherLocation(BuildingCode, floorCode);
        MDL.Location oLocation = new MDL.Location();
        List<MDL.Location> oLocations = new List<MDL.Location>();
        foreach (FAWebService.Location itm in arr)
        {
            oLocations.Add(new MDL.Location { Code = itm.Code, Description = itm.Description });
        }
        return oLocations;

    }