Use Model Display name for Blazor Validation message from Custom InputSelect

Question

As we know Blazor doesn't support Int option select for <InputSelect> (but support string & Enum) and we get the following error message:

Error: System.InvalidOperationException: Microsoft.AspNetCore.Components.Forms.InputSelect1[System.Nullable1[System.Int32]] does not support the type 'System.Nullable`1[System.Int32]'.

Therefore, I write a <CustomInputSelect>:

public class CustomInputSelect<TValue> : InputSelect<TValue>
    {
        protected override bool TryParseValueFromString(string value, out TValue result, out string validationErrorMessage)
        {
            if (typeof(TValue) == typeof(int?))
            {
                if (int.TryParse(value, out var resultInt))
                {
                    result = (TValue)(object)resultInt;
                    validationErrorMessage = null;
                    return true;
                }
                else
                {
                    result = default;
                    validationErrorMessage = $"The {FieldIdentifier.FieldName} field is Required.";
                    return false;
                }
            }
            else
            {
                return base.TryParseValueFromString(value, out result, out validationErrorMessage);
            }
        }
    }

I have the following Model:

public class Risk : ICloneable
    {
        /// <summary>
        /// Associated Legal Entity of the risk
        /// </summary>
        [Required]
        [Display(Name = "Legal Entity")]
        public int? LegalEntityId { get; set; }

        /// <summary>
        /// Associated Legal Entity Short Code of the risk
        /// </summary>
        [Required]
        [Display(Name = "Legal Entity Short Code")]
        public string LegalEntityShortCode { get; set; }
}

The following Blazor page:

    <CustomInputSelect id="ddlLegalEntity" class="form-control InputTextHeigth" @bind-Value="ShowRisk.LegalEntityId">
            @foreach (var option in LEList)
            {
                <option value="@option.Id">
                 @option.OptionName
                </option>
            }
    </CustomInputSelect>
<div class="cs-col-6">
    <ValidationMessage class="form-control" For="@(() => ShowRisk.LegalEntityId)" />
</div>

Everything is working fine. I can use int value on Option list. However, The validation error is generating as Field name instead of Display name. So I getting "The LegalEntityId field is Required." instead of "The Legal Entity field is Required".

From the first snapshot of the code, the message is generated:

validationErrorMessage = $"The {FieldIdentifier.FieldName} field is Required.";

How can I display Model Display name instead of FieldName?

github.com/dotnet/aspnetcore/issues/11414 This may have been resolved? — Alex

Bjorn De Rijcke Bjorn De Rijcke · Accepted Answer · 2021-02-25T10:16:12

Your CustomInputSelect inherits from InputSelect. InputSelect inherits from InputBase. This abstract class has a property called DisplayName.

It should be filled by either setting it manually in the razor file or via a Display attribute on your view model.

<InputDate @bind-Value="@moveOutViewModel.MoveOutDate" DisplayName="@localize["moveout_step_date_legend"]" />

or

[Display(Name = "address_street", ResourceType = typeof(Translations))]
public string Street { get; set; }

In your custom select class, you can use the following code:

if (int.TryParse(value, out var resultInt))
{
    result = (TValue)(object)resultInt;
    validationErrorMessage = null;
    return true;
}
else
{
    result = default;
    validationErrorMessage = $"The '{this.DisplayName ?? this.FieldIdentifier.FieldName}' field is required.";
    return false;
}

Use Model Display name for Blazor Validation message from Custom InputSelect

1 Answers