Controllers that take [FromQuery] types that are TypeConverters do not get validated when I use AbstractValidators.

I have a controller action like so:

        public async Task<ActionResult<List<ContactViewModel>>> Get([FromQuery]EntityIdList Id)
         =>  await _genericGet.GetMultipleByIdAsync(Id);

Where EntityIdList is this:

    [TypeConverter(typeof(EntityIdListTypeConverter))]
    public class EntityIdList : List<int>
    {
        public EntityIdList(IEnumerable<int> integers) : base(integers) { }
    }

The TypeConverter is a simple EntityIdListTypeConverter : TypeConverter which takes 1,2,3 and gives you List<int>(){1,2,3}. If the code is needed I can include it, but I removed for brevity.

This works with MVC without any further tweaks. Now, I moved to create an AbstractValidator like so:

public class EntityIdListValidator : AbstractValidator<EntityIdList> // I tried List<int> as well.
{
    public EntityIdListValidator()
    {
        RuleFor(x => x)
            .NotNull();

    }
}

But this validator never runs. My controller passes a null EntityIdList Id off to my service. I have other validators working so I know that my registrations are not the issue.

What am I missing?

[JeremySkinner]

Thanks for the example - this makes more sense to me now. I missed something important when I looked over your example. FluentVaidation cannot be run against a null instance.

FluentValidation is designed to validate properties of an object. The root instance itself cannot be null. In this case, FluentValidation will never be invoked as there is nothing to pass to it. If the EntityIds was a property of a different object with a NotNull rule against it, it would work fine but if you want to check that a root model is not null then you will need to do this outside FluentValidation (probably in the controller action).

[VictorioBerra]

Ah, yes I am using [ApiController].

@JeremySkinner here is a full repo https://github.com/VictorioBerra/fv-issue-977

All I did was dotnet new webapi && dotnet add package fluentvalidation.aspnetcore and then I added my typeconverter and wired up FV according to the docs.

You can see the values controller has two actions, one shows a complex object working perfectly with its abstractvalidator. The other using my EntityIdList. Even though I specified a notnull rule, it does not kick in. The controller action starts processing the request.