Question

I’m experimenting with ASP.NET MVC3 and want to simply populate a dropdown list with data I get from a LINQ2SQL class, like so

controller (I know, Linq doesn’t belong in the controller)

var allUsers = (from u in _userDataContext.Users
                            select u).ToList();
            ViewBag.allUsers = allUsers.ToList();
            return View();

view:

<select id="drop_heroes">
        @foreach (var u in ViewBag.allUsers)
        { 
            <option value="@u.pk_userid">@u.email</option>
        }
    </select>

That works fine, but I would like to use Razor @Html.Dropdownlist to create the same dropdown list, but can't find any info to make this work with Linq data. 

Answer 1

I know, Linq doesn’t belong in the controller

Then why are you using it in a controller? Anyway, at least it’s fine that you know it.

Here’s an example. As always in an ASP.NET MVC application you start by defining a view model which will represent the data that you need in the view. So in your case you need to display a dropdown so you define a list of users and a selected user id:

public class MyViewModel
{
    public string SelectedUserId { get; set; }
    public IEnumerable<SelectListItem> Users { get; set; }
}

then you define a controller action which will populate this view model from your repository and handle it to the view:

public ActionResult Index()
{
    var model = new MyViewModel
    {
        Users = _userDataContext.Users.ToList().Select(x => new SelectListItem
        {
            Value = x.pk_userid.ToString(),
            Text = x.email
        })
    }
    return View(model);
}

and finally you will have a view which will be strongly typed to your view model and use HTML helpers to generate the dropdownlist:

@model MyViewModel
@using (Html.BeginForm())
{
    @Html.DropDownListFor(x => x.SelectedUserId, Model.Users)
    <button type="submit">OK</button>
}

Things to notice:

• Usage of view models
• Usage of a strongly typed view
• Usage of strongly typed HTML helpers to generate markup such as form elements and input fields
• Getting rid of weakly typed structures such as ViewBag

If you follow these simple rules you will see how much easier your life as an ASP.NET MVC developer will become.