ASP.NET Core MVC model property binding is null

Question

I am using ASP.NET Core RC2 MVC with Entity Framework and trying to save a new car. The problem is, that in the create method of the car controller the property Color is null when the action is posted back. All other properties/fields are set. But the Color which refers to the CarColors model is null.

The CarColor model

public class CarColor
{
    [Key]
    public int CarColorId { get; set; }

    [MinLength(3)]
    public string Name { get; set; }

    [Required]
    public string ColorCode { get; set; }
}

The main model Car

public class Car
{
    [Key]
    public int CarId { get; set; }

    [MinLength(2)]
    public string Name { get; set; }

    [Required]
    public DateTime YearOfConstruction { get; set; }

    [Required]
    public CarColor Color { get; set; }
}

The Cars controller

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create([Bind("Color,Name,YearOfConstruction")] Car car)
{
    if (ModelState.IsValid)
    {
        _context.Add(car);
        await _context.SaveChangesAsync();
        return RedirectToAction("Index");
    }
    return View(car);
}

The request data:

Debugging screenshot of the posted car

Can u give me a helping hand, how the property could be "bound" and so the ModelState.IsValid == true?

Despite ASP.NET 5, this may help lbadri.wordpress.com/2014/11/23/… — Set
– Set, Commented Jun 9, 2016 at 14:09
You're submitting an ID and expecting it to populate, that's not how ASP.NET Binding works or has ever worked? If you want the whole model, you have to submit the whole model. Otherwise post back an ID and load the model server side. — Rudi Visser
– Rudi Visser, Commented Jun 9, 2016 at 14:54

Yury Scherbakov · Accepted Answer · 2016-06-09 17:13:06Z

3

If you want populate Color property of your Car model, your request must looks like:

[0] {[Name, Volvo]}
[1] {[Yearof Construction, 19/16/2015]}
[2] {[Color.CarColorId, 3]} (will be "bound" only ID)

It means: name of your input/select on the View must be "Color.CarColorId".

... But you chose incorrect way. You should not use Domain models in your View directly. You should create View Models special for View and for incoming properties of you action methods.

correct way

domain models (without changes):

public class CarColor
{
    [Key]
    public int CarColorId { get; set; }

    [MinLength(3)]
    public string Name { get; set; }

    [Required]
    public string ColorCode { get; set; }
}

public class Car
{
    [Key]
    public int CarId { get; set; }

    [MinLength(2)]
    public string Name { get; set; }

    [Required]
    public DateTime YearOfConstruction { get; set; }

    [Required]
    public CarColor Color { get; set; }
}

View model:

public class CarModel
{    
    [MinLength(2)]
    public string Name { get; set; }

    [Required]
    public DateTime YearOfConstruction { get; set; }

    [Required]
    public int ColorId { get; set; }    
}

Controller:

[HttpPost]
[ValidateAntiForgeryToken]
public async Task<IActionResult> Create(CarModel model)
{
    if (ModelState.IsValid)
    {
        var color = await _context.Colors.FirstAsync(c => c.CarColorId == model.ColorId, this.HttpContext.RequestAborted);
        var car = new Car();
        car.Name = model.Name;
        car.YearOfConstruction = model.YearOfConstruction;
        car.Color = color;

        _context.Cars.Add(car);
        await _context.SaveChangesAsync(this.HttpContext.RequestAborted);
        return RedirectToAction("Index");
    }
    return View(car);
}

edited Jun 9, 2016 at 17:13

answered Jun 9, 2016 at 16:44

Yury Scherbakov

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2 Comments

serious Over a year ago

Thanks for the detailed information! Works like a charm.

JustADev Over a year ago

So when using a ViewModel, we cannot use: [Bind("Color,Name,YearOfConstruction")] with parameter in Controller save function?

Machet · Accepted Answer · 2018-07-06 15:12:40Z

0

In my case I had auto generated internal set properties on my model class. Framework couldn't bind those. Maybe this post will help someone in future as it took me a while to figure this out ;)

answered Jul 6, 2018 at 15:12

Machet

1,1108 silver badges17 bronze badges

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