ASP MVC Binding Variable number of dropDownLists

Question

I need to bind a variable number of dropdownlists, how do I achieve this?

In my project, until now I have only had to deal with binding to a known number of dropdown lists. To do this I have simply done the below:

viewModel

//for staff ddl
public List<Staff> Staff { get; set;     
public int? SelectedStaffId { get; set; }
public IEnumerable<System.Web.Mvc.SelectListItem> StaffItems
{
    get { return new System.Web.Mvc.SelectList(Staff, "StaffID", "FirstName"); }
}//end

view

@Html.DropDownListFor(m => m.SelectedStaffId, Model.StaffItems, "--Who is taking appointment--", new { @class = "form-control", @id = "ddlValuer" })

Now I want to bind a variable number of dropdownlists. I expected to achieve this would be a simple loop as below: (BUT THIS DOESN'T WORK)

ViewModel

//for offerState ddl
public List<OfferState> OfferStates { get; set; }
public int? SelectedOfferStateId { get; set; }
public IEnumerable<System.Web.Mvc.SelectListItem> OfferStateItems
{
    get { return new System.Web.Mvc.SelectList(OfferStates, "OfferStateID", "Description"); }
}//end

View

for (var i = 0; i < Model.Offers.Count; i++)
{
    <div class="row">
        <div class="col-lg-4">@Html.TextBoxFor(m => Model.Offers[i].Offer1, null, new { @class = "form-control", @disabled = "disabled" })</div>
        <div class="col-lg-8">@Html.DropDownListFor(m => Model.Offers[i].OfferStateID, Model.OfferStateItems, "--State--", new { @class = "form-control" })</div>
    </div>
}

The items are never selected, --state-- (the default text), is always displayed. I have stepped through the code and can see there are three items with an OfferStateID.

Why is the default value always selected? Is there a better way?

try to use Html.ListBoxFor instead of Html.DropDownListFor http://stackoverflow.com/questions/12176735/getting-multiple-selected-values-in-html-dropdownlistfor — StepUp, Apr 01 '16 at 21:37

score 1 · Accepted Answer · 2016-04-01T22:14:38.353

1

This is a known limitation of using DropDownListFor() in a loop. You need to build a new SelectList in each iteration, or use an EditorTemplate and pass the SelectList to the template as AdditionalViewData

for (var i = 0; i < Model.Offers.Count; i++)
{
    @Html.DropDownListFor(m => m.Offers[i].OfferStateID, new SelectList(Model.OfferStateItems, "OfferStateID", "Description", Model.Offers[i].OfferStateID), "--State--", new { @class = "form-control" })
}

where OfferStateItems is IEnumerable<OfferStates> (not SelectList)

edited Apr 01 '16 at 22:14

answered Apr 01 '16 at 21:40

thanks for the suggestion. I have tried it and my problem persists – tony09uk Apr 01 '16 at 21:57

score 0 · Answer 2 · answered Apr 01 '16 at 21:42

In your model just change this:

 public IEnumerable<System.Web.Mvc.SelectListItem> OfferStateItems
{
    get { return new System.Web.Mvc.SelectList(OfferStates, "OfferStateID",     "Description"); }
}//end

To this

public List<OfferStates> OfferStateItems{get;set;}

Then create a constructor for your ModelView

public yourViewModel()
{
      this.OfferStateItems=(place here the method to populate the list)
}

Then you can use that list with the items you need, and use a HTML helper to write the items.

ASP MVC Binding Variable number of dropDownLists

2 Answers2