ASP.NET Core MVC SelectList not setting selectedValue

Question

In ASP.NET Core MVC, I'm trying to set the pre-selected value for a SelectList - something which I thought would be a simple task, but it's driving me bonkers!

My controller contains the following:

ViewData["Scores"] = GetScoresAsSelectList();

and

private SelectList GetScoresAsSelectList()
{
    var scores =
        Enumerable.Range(0, 6)
        .Select(score => new
        {
            Value = score.ToString(),
            Text = Helper.ConvertScoreToText(score) // gets some unique text back
        })
       .OrderBy(o => o.Value)
       .ToList();
    scores.Insert(0, new { Value = string.Empty, Text = "Please select a value" });
    return new SelectList(scores, "Value", "Text", scores.FirstOrDefault().Value);
}

My view contains:

@{ var FieldScoreId = Guid.NewGuid(); }
<div class="form-group col-md-3">
    <label asp-for="FieldScore" class="control-label"></label>
    <select asp-for="FieldScore" class="form-control" asp-items="ViewBag.Scores" id="@FieldScoreId"></select>
    <span asp-validation-for="FieldScore" class="text-danger"></span>
</div>

The output (rendered HTML) is:

<select class="form-control" id="1fce2ac1-e63c-4b85-b69a-14b7713eafaf" data-val="true" data-val-range="The field Field Score must be between 0 and 5." data-val-range-max="5" data-val-range-min="0" data-val-required="The Field Score field is required." name="FieldScore">
<option value="">Please select a value</option>
<option selected="selected" value="0">None (0)</option>   <!-- WHY (OH WHY!?) IS THIS SELECTED? -->
<option value="1">1-Score (1)</option>
<option value="2">2-Score (2)</option>
<option value="3">3-Score (3)</option>
<option value="4">4-Score (4)</option>
<option value="5">5-Score (5)</option>
</select>

I've tried replacing scores.FirstOrDefault().Value with "". If Enumerable.Range(0, 6) was replaced with Enumerable.Range(1, 6) (start the range at 1, not 0), Please select a value would be selected.

I cannot figure out what the problem is, and it's driving me insane! :)

Many thanks for your help

When used on a select that is bound to a model property, the selected item will have a Value equal to the value of that property. The selected value set on the SelectList will be ignored. — Johnathan Barclay
– Johnathan Barclay, Commented Sep 17, 2020 at 15:45
Thanks @JohnathanBarclay - it makes sense now you've said it :) — danwag
– danwag, Commented Sep 17, 2020 at 18:00
@danwag: what @Johnathan said is correct. And I would like to add: since you're passing a view model to the view already, you can define a list there to contain all the possible options, instead of use a ViewBag. You shouldn't add "Please select a value" to the option list though. Instead, you can define that option in the view: <select asp-for=""><option value>- select -</option></select> — David Liang
– David Liang, Commented Sep 17, 2020 at 18:06
Thanks @DavidLiang. Normally I would pass the select list in a view model, rather than in the ViewBag, but the pattern has already been established in code :). A great idea to add the <option> inside the <select> in the view, rather than adding it to the model. — danwag
– danwag, Commented Sep 17, 2020 at 18:18

danwag · Accepted Answer · 2020-09-17 19:30:10Z

Thank you to @JohnathanBarclay for leading me down the right path.

I changed my controller to the following:

private SelectList GetScoresAsSelectList()
{
    var scores =
        Enumerable.Range(0, 6)
        .Select(score => new
        {
            Value = score,  //changed from string to int
            Text = Helper.ConvertScoreToText(score) // gets some unique text back
        })
       .OrderBy(o => o.Value)
       .ToList();
    scores.Insert(0, new { Value = -1/* changed from "" to -1 */, Text = "Please select a value" });
    return new SelectList(scores, "Value", "Text", scores.FirstOrDefault().Value);
}

Also in the controller, in the Add GET method, I set FieldScore to -1. Works well: the dropdown defaults to "please select" and the dropdown has to be changed from "please select" as the model requires a range between 0 and 5.

Collectives™ on Stack Overflow

ASP.NET Core MVC SelectList not setting selectedValue

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related