Can FluentValidation can do checkboxes?

Question

I'm using FluentValidation to validate input on an MVC form.

I have a checkbox.

No matter what I set the validation rule to, it does not validate the checkbox.

I know validation is working, because I have a dropdownlist that's validating fine on the same page.

View

<%: Html.CheckBoxFor(m => m.fullname_required) %>

Model

[Validator(typeof(CreateFormModelValidator))]
public class CreateFormModel
{
    public int? group_id { get; set; }

    public IEnumerable<SelectListItem> Groups { get; set; }

    [DisplayName("Fullname is required")]
    public bool fullname_required { get; set; }
}
public class CreateFormModelValidator : AbstractValidator<CreateFormModel>
{
    public CreateFormModelValidator()
    {
        RuleFor(x => x.group_id).NotEmpty().NotNull().WithMessage("Please select a group!");
        RuleFor(x => x.fullname_required).NotNull();        
    }
}

I've tried

RuleFor(x => x.fullname_required).NotEmpty();
RuleFor(x => x.fullname_required).NotNull();
RuleFor(x => x.fullname_required).NotEqual(false); 

None of which work. I'm going bananas trying to make this work. It's an F***ing checkbox

PS: I've found threads talking about using jQuery instead, but this is using server side validation, not client side.

Answer 1

I never placed the ValidationMessageFor attribute on the page for the checkbox. It was validating fine, but I couldn't see it.

UPDATE: The eventual goal was to have one checkbox which is only validated if a second checkbox is checked. Ie

RuleFor(x => x.fullname_show).NotEmpty().When(x => x.fullname_required == true);

However, this still wouldn't work after the facepalm above, but thanks to lomaxx I was able to get it working by converting fullname_required to bool?

RuleFor(x => x.fullname_show).NotEmpty().When(x => ((bool?)x.fullname_required) != false);

If anyone is trying to conditionally validate a checkbox using FluentValidation in MVC, THAT'S how you do it!

Answer 2

I have a theory, and I could be wrong, but a bool is a value type, not a reference type, so by definition it always has a value (i.e. true or false).

So when you're submitting the form, it sees it has a value of false for "unchecked" and assumes that's a valid value.

What you might need to do is change the bool to be nullable in your code so that the default value is "null" rather than false.