multiple select list c# mvc

Question

I am trying to create a multiple select from a single select drop down menu. my model originally had:

public int country_id { get; set; }

and my view had:

 @Html.DropDownList("country_id", String.Empty)

to change it to multiple select i changed my model to:

public List<Country> country_id { get; set; }

and my view to:

@Html.ListBoxFor(model => model.country_id, ViewBag.ActionsList as MultiSelectList, new { @class = "multiselect", @style = "width: 450px;height:200px" })

the problem i am having is updating my databse using migration since the i am changing int to list, however, it keeps saying

"Cannot drop the index 'dbo.People.IX_country_id', because it does not exist or you do not have permission."

I do have permission so I am not sure if I am missing something?

My list of countries is coming straight from the country database.

thanks for your inputs.

What is the question about ? The problem with the index or the view? — Pleun
– Pleun, Commented Nov 27, 2014 at 15:47
the problem is when i do the database migration to update from int to a list, it is not updating it. so the model doesn't get updated. — NULL
– NULL, Commented Nov 27, 2014 at 17:09

markpsmith · Accepted Answer · 2014-11-28 09:34:43Z

1

You need to populate a selectlist in the controller & pass it to the view, something like this:

var countries = from d in db.Countries
                        select new
                        {
                            Id = d.Id,
                            Name = d.Name
                        };
// I'd pass this in a model, but use ViewBag if that's what you're familiar with
ViewBag.ActionsList =  new SelectList(countries , "Id", "Name");

And in the View:

@Html.DropDownListFor(model => model.country_id, ViewBag.ActionsList)

UPDATE:

You should use a ViewModel for this:

public class CountryList
{
    // this may have to be a List<SelectListItems> to work with MultiSelectList - check.
    public SelectList Countries{ get; set; }
    public List<int> SelectedCountryIds { get; set; }
}

In the controller:

var model = new CountryList
{
    SelectList = //assign the selectlist created earlier
}
return View(model);

In the View:

@Html.ListBoxFor(m => m.SelectedCountryIds, new MultiSelectList(@Model.Countries, "Id", "Name", @Model.SelectedCountryIds))

edited Nov 28, 2014 at 9:34

answered Nov 27, 2014 at 15:44

markpsmith

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6 Comments

NULL Over a year ago

the problem is when i do the database migration to update from int to a list, it is not updating it. so the model doesn't get updated.

markpsmith Over a year ago

Don't update it to a list, that won't work. It needs to stay as an int.

NULL Over a year ago

i have another question, so if i am not updating to a list, how do i store/save the selected lists from the drop down?

markpsmith Over a year ago

I see why you were trying update the Id to List - I've update the answer

NULL Over a year ago

this is wonderful. so i need my regular database model, and a view model:-) bingo, thanks.

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