How can I insert null value into a nullable enum property using a select list in a view?

Question

I have set my enum property as nullable in my model but when I submit my create form I get 'The value 'Select' is not valid for productColor.'

My Model:

  public class product
    {
        public int productId { get; set; }
        public string productName { get; set; }
        public color? productColor { get; set; }
    }

    public enum color
    {
        Red, Green, Blue
    }

My Create View:

            <div class="form-group">
                <label asp-for="productColor" class="control-label"></label>
                <select asp-for="productColor" asp-items="@Html.GetEnumSelectList<color>()" class="form-control">
                 <option>Select</option>
                </select>
                <span asp-validation-for="productColor" class="text-danger"></span>
            </div>

My Controller:

public async Task<IActionResult> Create([Bind("productId,productName,productColor")] product product)
        {
            if (ModelState.IsValid)
            {
                _context.Add(product);
                await _context.SaveChangesAsync();
                return RedirectToAction(nameof(Index));
            }
            return View(product);
        }

Result:

The form appears to post null for the productColor value but the model state is invalid at the controller and the view returns with 'The value 'Select' is not valid for productColor.'

You might consider make a "not applicable" or "None" enum value instead of trying to make no selection — Crowcoder
– Crowcoder, Commented Feb 4, 2019 at 11:56

Oleksandr · Accepted Answer · 2019-02-04 12:09:39Z

9

Update your option element by adding empty value tag

<select asp-for="productColor" asp-items="@Html.GetEnumSelectList<color>()" class="form-control">
        <option value="">Select</option> <!-- notice value="" -->
</select>

If there is not value tag specified browser sends inner text of option as a selected value. So in your case browser sends Select values which is not suitable for controller. This code instructs browser to send empty value which is successfully converted to null in ASP.NET.

edited Feb 4, 2019 at 12:09

answered Feb 4, 2019 at 12:04

Oleksandr

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