How to preselect MVC Dropdownlistfor?

Question

I have multiple dropdownlists on a page which are being built at runtime. I have a view model with a selectlist. I have tried this post which is great but it is a bit different coz i have a collection of view model on the view. I think I am close but i am not sure how to use DropDownListFor properly. How can I preselect each dropdownlist with different values?

VM

public class categoryVm
{        
    public IEnumerable<SelectListItem> category { get; set; }

    public string SelectedValue { get; set; }
}

View

@model IEnumerable<categoryVm>
@foreach (var item in Model)
{
   //i think i am missing something here???
   @Html.DropDownListFor(**x => item.SelectedValue**, item.category)
}

Controller

name is one of StaticName and it's like an Id and it's in the list.

var categories = new List<categoryVm>();
var selectlistcolumns = columns.Select(x => new SelectListItem
            {                    
                Value = x.StaticName,
                Text = x.DisplayName
            });

foreach (var column_loopVariable in dtCSV.Columns)
            {
                var category= new categoryVm();                    
                category.category= selectlistcolumns;
                category.SelectedValue = "name";
                categories .Add(category);
            }
     return View(categories);

I would prefer mvc solution than using javascript changing dom.

You can preselect a DDL value the same way you would pre populate a TextBox value. Make sense? — CSharper, Apr 02 '14 at 15:34

score 3 · Answer 1 · answered Apr 02 '14 at 10:03

Try this

var selectlistcolumns = columns.Select(x => new SelectListItem
        {                    
            Value = x.StaticName,
            Text = x.DisplayName,
            Selected = x.DisplayName == "name"  // this sets the selected value
        });

foreach (var column_loopVariable in dtCSV.Columns)
        {
            var category= new categoryVm();                    
            category.category= selectlistcolumns;
            //category.SelectedValue = "name"; // not required
            categories .Add(category);
        }

Also if you notice the signature for Html.DropDownListFor(propExpresstion, selectList) so the first argument as you assumed does not set the selected value. Hope this helps!

score 1 · Answer 2 · edited May 23 '17 at 11:58

1

Since your controller return List. You should use IList in view page instead of IEnumerable.

@model IList<categoryVm>

for (int i = 0; i < Model.Count; i++) 
{
   @Html.DropDownListFor(m => Model[i].SelectedValue, Model[i].category)
}

View Model IEnumerable<> property is coming back null (not binding) from post method?

edited May 23 '17 at 11:58

Community

1
1

answered Apr 02 '14 at 09:58

Ashwini Verma

7,477
6
36
56

1

Either this method, or another option is to make an EditorTemplate for "categoryvm", in which case you can simply call Html.EditorFor and MVC will automatically apply proper indexing to your fields – Moeri Apr 02 '14 at 10:01

score 0 · Answer 3 · edited Apr 02 '14 at 10:06

0

@Html.DropDownListFor(m => item.SelectedValue, new SelectList(item.category))

edited Apr 02 '14 at 10:06

DHN

4,807
3
31
45

answered Apr 02 '14 at 09:37

Murali Murugesan

22,423
17
73
120

thanks for your reply Murali. m => item.category doesn't have SelectedValue in intellisense .. m => item has SelectedValue but that doesn't work. – Laurence Apr 02 '14 at 09:44
@LaurenceNyein, it was my mistake. Edited answer. – Murali Murugesan Apr 02 '14 at 09:51
Thanks for your help but i don't see any difference to my original code .. can you explain a bit more please? – Laurence Apr 02 '14 at 09:56

How to preselect MVC Dropdownlistfor?

3 Answers3