Fluent Validation Inconsistent with ASP.NET MVC 5

Question

I'm using Fluent Validation v5.5 with ASP.NET v5.2.2 and I'm getting some inconsistent results with the validation.

My view model is:

public class QuoteViewModel
{
    [Display(Name = @"Day")]
    public int DateOfBirthDay { get; set; }

    [Display(Name = @"Month")]
    public int DateOfBirthMonth { get; set; }

    [Display(Name = @"Year")]
    public int DateOfBirthYear { get; set; }

    [Display(Name = @"Gender")]
    public Gender? Gender { get; set; }

    [Display(Name = @"State")]
    public int StateId { get; set; }
}

My controller method is:

public ActionResult Quote(QuoteViewModel viewModel)
{
    var _validator = new QuoteValidator();
    var results = _validator.Validate(viewModel);

    if (!ModelState.IsValid)
    {
        return Json(false);
    }

    return Json(true);
}

My validator is:

public class QuoteValidator : AbstractValidator<QuoteViewModel>
{
    public QuoteValidator()
    {
        RuleFor(x => x.Gender).NotEmpty();
        RuleFor(x => x.StateId).NotEmpty();
        RuleFor(x => x.DateOfBirthDay).NotEmpty().InclusiveBetween(1, 31);
        RuleFor(x => x.DateOfBirthMonth).NotEmpty().InclusiveBetween(1, 12);
        RuleFor(x => x.DateOfBirthYear).NotEmpty().LessThanOrEqualTo(DateTime.UtcNow.Year);
    }
}

I'm running a test that posts all blank value form fields. Thus the view model fields retain default values after the view model object is created.

For comparison, in the controller I'm running the validation explicitly and the results aren't consistent with the validation result in ModelState.

ModelState is showing 4 errors, all triggered by NotEmpty rules. NotEmpty on the nullable enum Gender doesn't seem to trigger.

The explicit validation is returning 7 out of 8 errors, the LessThanOrEqualTo rule won't fire since the DateOfBirthYear defaults to zero.

My pain point is I can't figure out why ModelState is missing the NotEmpty error on the nullable enum Gender.

The only way I've been able to trigger that error is to post just the Gender value.

Please help.

EDIT:

After stepping through some code, it appears that the issue is related to the Fluent Validation RequiredFluentValidationPropertyValidator. The Gender field is a nullable value type which is bound to null. The following snippet from RequiredFluentValidationPropertyValidator prevents validation:

ShouldValidate = isNonNullableValueType && nullWasSpecified;

why not simply chech this RuleFor(x => x.Gender).NotNull() ? — Zinov
– Zinov, Commented Jul 12, 2017 at 18:57

Alex Art. · Accepted Answer · 2014-12-06 12:07:01Z

1

!ModelState.IsValid doesn't use your validation result it uses defaulf MVC validation (that can be added through DataAnnotations). You have to check !results.IsValid instead which contains the validation result of your QuoteValidator.

If you want to use default ModelState.IsValid you have to mark your model with validator attribute:

[Validator(typeof(QuoteValidator))]
public class QuoteViewModel
{
    [Display(Name = @"Day")]
    public int DateOfBirthDay { get; set; }

    [Display(Name = @"Month")]
    public int DateOfBirthMonth { get; set; }

    [Display(Name = @"Year")]
    public int DateOfBirthYear { get; set; }

    [Display(Name = @"Gender")]
    public Gender? Gender { get; set; }

    [Display(Name = @"State")]
    public int StateId { get; set; }
}

And add the following line to your Application_Start method:

protected void Application_Start() {
    FluentValidationModelValidatorProvider.Configure();
}

edited Dec 6, 2014 at 12:07

answered Dec 6, 2014 at 12:00

Alex Art.

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1 Comment

Rudy Over a year ago

The crux of my question has to do with the fact that the nullable Gender field isn't being validated. I'm just including the explicit validation "results" to compare. The code I've shown above is contrived to illustrate the inconsistency in the validation. My Application_Start method includes the code you've noted above so Fluent Validation is fully integrated as the validation provider.

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