Getting Runtime Error With Drop Down List From Database MVC4

Question

I am trying to create a drop down list in MVC4 derived from a database model called 'SiteTableBookings', the runtime error is:

"An exception of type 'System.NullReferenceException' occurred in App_Web_e3cawdyt.dll but was not handled in user code"

Basically the application requires a drop down list for bookings of flights, I have searched many methods on how to achieve a drop down list online and have not been able to get the application to run.

New to MVC4 and still learning any help would be much appreciated.

Model:

public partial class SiteBookingsTable
{
    public int listID { get; set; }
    public string departureAirport { get; set; }  
    public string chooseDepartureAirport { get; set; }     

    public IEnumerable<SiteBookingsTable> selectDeparture = new List<SiteBookingsTable>
    {
        new SiteBookingsTable {listID = 0, departureAirport = "London (LTN)"},
        new SiteBookingsTable {listID = 1, departureAirport = "Manchester (MAN)"}
    };
}

View:

<tr>
   <td>@Html.LabelFor(model => model.chooseDepartureAirport)<br /> 
       @Html.DropDownListFor(model => model.chooseDepartureAirport,
        new SelectList(Model.selectDeparture, "listID", "departureAirport")) </td>
</tr>

Controller:

public ActionResult Create()
{           
    return View();
}

Racil Hilan · Accepted Answer · 2014-04-07 15:22:53Z

I would create the list in the controller rather than the model.

Model:

public partial class SiteBookingsTable
{
    public int listID { get; set; }
    public string departureAirport { get; set; }  
    public string chooseDepartureAirport { get; set; }     

    public IEnumerable<SelectListItem> selectDeparture { get; set; }
}

View:

<tr>
   <td>@Html.LabelFor(model => model.chooseDepartureAirport)<br /> 
       @Html.DropDownListFor(model => model.chooseDepartureAirport,
                             Model.selectDeparture)
   </td>
</tr>

Controller:

public ActionResult Create()
{
    IEnumerable<SiteBookingsTable> selectDeparture = new List<SiteBookingsTable>()
    {
        new SiteBookingsTable {listID = 0, departureAirport = "London (LTN)"},
        new SiteBookingsTable {listID = 1, departureAirport = "Manchester (MAN)"}
    };

    model = new SiteBookingsTable()
    model.selectDeparture = new SelectList(selectDeparture, "listID", "departureAirport");

    return View(model);
}

JMK · Accepted Answer · 2014-04-07 15:21:00Z

0

I think you need to make the selectDeparture field static like so:

public static IEnumerable<SiteBookingsTable> selectDeparture = new List<SiteBookingsTable> 
{ 
    new SiteBookingsTable { listID = 0, departureAirport = "London (LTN)" }, 
    new SiteBookingsTable { listID = 1, departureAirport = "Manchester (MAN)" } 
};

And then update your dropdown list to use this static property, and to point at the departureAirport property:

@Html.DropDownListFor(model => model.departureAirport,
    new SelectList(SiteBookingsTable.selectDeparture, "listID", "departureAirport"))

answered Apr 7, 2014 at 15:21

JMK

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