implementing dropdownlist in asp.net mvc 3

Question

I am teaching myself asp .net mvc3. I have researched a lot but the more I read the more confused I become. I want to create a page where users can register their property for sale or rent.

I have created a database which looks like this:

public class Property
    {
        public int PropertyId { get; set; }
        public int PropertyType { get; set; }
        ···
        public int Furnished { get; set; }
        ...
}

Now, I want dropdownlistfor = PropertyType and Furnished.

Property type would be 1 Flat 2 House 3 Detached House ...

Furnished would be: 1 Furnished 2 UnFurnished 3 PartFurnished ...

Now, I am really not sure where to keep this information in my code. Should I have 2 tables in my database which store this lookup? Or should I have 1 table which has all lookups? Or should I just keep this information in the model?

How will the model bind to PropertyType and Furnished in the Property entity?

Thanks!

Answer 1

By storing property types and furnished types in the database, you could enforce data integrity with a foreign key, rather than just storing an integer id, so I would definitely recommend this.

It also means it is future proofed for if you want to add new types. I know the values don't change often/will never change but if you wanted to add bungalow/maisonette in the future you don't have to rebuild and deploy your project, you can simply add a new row in the database.

In terms of how this would work, I'd recommend using a ViewModel that gets passed to the view, rather than passing the database model directly. That way you separate your database model from the view, and the view only sees what it needs to. It also means your drop down lists etc are strongly typed and are directly in your view model rather than just thrown into the ViewBag. Your view model could look like:

public class PropertyViewModel
{
    public int PropertyId { get; set; }

    public int PropertyType { get; set; }
    public IEnumerable<SelectListItem> PropertyTypes { get; set; }

    public int Furnished { get; set; }
    public IEnumerable<SelectListItem> FurnishedTypes { get; set; }
}

So then your controller action would look like:

public class PropertiesController : Controller
{
    [HttpGet]
    public ViewResult Edit(int id)
    {
        Property property = db.Properties.Single(p => p.Id == id);

        PropertyViewModel viewModel = new PropertyViewModel
            {
                PropertyId = property.Id,
                PropertyType = property.PropertyType,
                PropertyTypes = from p in db.PropertyTypes
                                orderby p.TypeName
                                select new SelectListItem
                                    {
                                        Text = p.TypeName,
                                        Value = g.PropertyTypeId.ToString()
                                    }
                Furnished = property.Furnished,
                FurnishedTypes = from p in db.FurnishedTypes
                                orderby p.TypeName
                                select new SelectListItem
                                    {
                                        Text = p.TypeName,
                                        Value = g.FurnishedTypeId.ToString()
                                    }

            };

        return View();
    }

    [HttpGet]
    public ViewResult Edit(int id, PropertyViewModel propertyViewModel)
    {
        if(ModelState.IsValid)
        {
            // TODO: Store stuff in the database here
        }

        // TODO: Repopulate the view model drop lists here e.g.:
        propertyViewModel.FurnishedTypes = from p in db.FurnishedTypes
                                orderby p.TypeName
                                select new SelectListItem
                                    {
                                        Text = p.TypeName,
                                        Value = g.FurnishedTypeId.ToString()
                                    };

        return View(propertyViewModel);
    }
}

And your view would have things like:

@Html.LabelFor(m => m.PropertyType)
@Html.DropDownListFor(m => m.PropertyType, Model.PropertyTypes)

Answer 2

I usually handle this sort of situation by using an enumeration in code:

public enum PropertyType {
    Flat = 1,
    House = 2,
    Detached House = 3
}

Then in your view:

<select>
@foreach(var val in Enum.GetNames(typeof(PropertyType)){
    <option>val</option>
}
</select>

You can set the id of the option equal to the value of each item in the enum, and pass it to the controller.

EDIT: To directly answer your questions: You can store them as lookups in the db, but for small unlikely to change things, I usually just use an enum, and save a round trip.

Also look at this approach, as it looks better than mine: Converting HTML.EditorFor into a drop down (html.dropdownfor?)