Question

I have a model with a List<System.Drawing.Color>, as I mentioned, which comes to use in the Seed() like this:

    protected override void Seed(DatabaseContext context)
    {
        var somethings = new List<Something>
        {
            new Something
            {
                Name="blah blah", Colors= { Color.Black, Color.Red }
            }
        };
    }

And as long as I have the Colors over there like that, I always recieve
Object reference not set to an instance of an object. at line var somethings = new List<Something>.

When I remove the Colors, it goes away and everything works perfectly, what causes this and how can I solve this problem?

Thanks.

EDIT:

Something‘s model:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Drawing;

namespace MVCApplication7
{
    public class Something
    {
        public int SomethingID { get; set; }
        public string Name { get; set; }
        public List<Color> Colors { get; set; }
    }
}

Controller:

    ........
    private DatabaseContext db = new DatabaseContext();

    //
    // GET: /Home/

    public ViewResult Index()
    {
        return View(db.Somethings.ToList());
    }

View: (I’m sure it’s irrelavent because the debugger shows the Colors is empty.

        @foreach (var itemColor in item.Colors)
        {
            Html.Raw(itemColor.ToString());
        }

Global.asax

    .........
    protected void Application_Start()
    {
        AreaRegistration.RegisterAllAreas();

        RegisterGlobalFilters(GlobalFilters.Filters);
        RegisterRoutes(RouteTable.Routes);

        Database.SetInitializer<DatabaseContext>(new DatabaseInitializer());
    }

Answer 1

Chances are your Something constructor is returning without setting the Colors property to an empty list. Your collection initializer is just calling Colors.Add(Color.Black) and then Colors.Add(Color.Red) – that’s not going to work if the Colors property is returning a null reference.

Either set it to an empty list to start with (e.g. in the constructor) or create a new list and set the property itself:

new Something
{
    Name = "blah blah",
    Colors = new List<Color> { Color.Black, Color.Red }
}

It’s important that you understand the difference between the above code and your original. Your code is currently equivalent to (within the List<Something> collection initializer):

Something tmp = new Something();
tmp.Name = "blah blah";
tmp.Colors.Add(Color.Black);
tmp.Colors.Add(Color.Red);
// Now add tmp to the list we're building.

My code above is equivalent to:

Something tmp = new Something();
tmp.Name = "blah blah";
List<Color> tmp2 = new List<Color>();
tmp2.Add(Color.Black);
tmp2.Add(Color.Red);
tmp.Colors = tmp2;
// Now add tmp to the list we're building

See the difference?