Entity Framework ASP.NET MVC private model fields

Question

There is a field in our database which really ought to be a boolean, but for some reason the original developers made it a CHAR which will either be set to "1" or "0".

    [Column("CHARGEABLE")]
    [StringLength(1)]
    private string Chargeable { get; set; }

I want my model to represent this field as a boolean so I figured I could add a property to my model to wrap it:

    [NotMapped]
    public bool ChargeableTrue
    {
        get
        {
            return Chargeable == "1" ? true : false;
        }
        set
        {
            Chargeable = value ? "1" : "0";
        }
    }

Now on my View I just display the EditorFor ( ChargeableTrue ), but when I click save it doesn't actually update it.

I think what is happening is that when the model is being updated, it's still attempting to get the value of 'Chargeable' from the View, even though I haven't displayed it there. And since there is no input field, it just gets null and ends up saving that to the database.

        if (ModelState.IsValid)
        {
            db.Entry(call).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }

What is one expected to do in this situation?

score 2 · Answer 1 · answered Jan 08 '12 at 20:51

2

Use a view model and make your mapping on the controller.

answered Jan 08 '12 at 20:51

Per Kastman

4,466
24
21

This is what I'd do when your domain doesn't really match what you want on your views. +1 – kamranicus Jan 08 '12 at 21:47
This is what I ended up doing and now I have more problems than I started with. – NoPyGod Jan 09 '12 at 04:02
How do I "make my mapping" ? Do you mean manually updating each field of the model object with the fields from the view model? – NoPyGod Jan 09 '12 at 04:13
@subkamran that question was for you (I forgot to put your name in it). Would really appreciate any advice you could offer. – NoPyGod Jan 09 '12 at 04:25
I typically use a tool like [AutoMapper](https://github.com/AutoMapper/AutoMapper). So, `Mapper.Map(viewModel)` as an example; cuts down on the amount of manual mapping you need to do. See also: http://stackoverflow.com/questions/5306655/using-view-models-in-asp-net-mvc-3 – kamranicus Jan 09 '12 at 04:46

score 2 · Accepted Answer · answered Jan 08 '12 at 21:53

Based on KMan's answer, here's the extended version just in case you're not familiar with creating view models.

The idea is that your domain object is not really what you want to be updating exactly from your views. Instead, you create a go-between that can also include view-specific items (like a list of objects to populate a drop-down).

public class MyViewModel {
    public bool Chargeable { get; set; }
}

Now you can do this:

@* In view *@
Html.EditorFor(m => m.Chargeable)

// In controller
public ActionResult Save(MyViewModel model) {
    if (ModelState.IsValid) {
        var domainObject = new MyObject() {
            Chargeable = model.Chargeable ? "1" : "0"
        };

        // the rest of your code using domainObject
    }
}

I'd consider just creating an overload of your domain object's constructor that accepts your view model to keep the mapping in one place. I typically use a tool like AutoMapper to map objects or manual extension methods.

A view model typically contains a sub-set of your domain object's properties, but can contain all of them or more properties like lists, visbility states, etc. They come in incredibly useful and I've never done a MVC project where I haven't used them.

Entity Framework ASP.NET MVC private model fields

2 Answers2