Add custom state during custom validation

Question

I created a custom validation rule in FluentValidation, but I am unable to figure out how to add a custom state to the error:

RuleFor(x => x.MyField).Custom((myField, context) =>
{
    switch (myField)
    {
        // ...

        default:
            context.AddFailure($"Unexpected value for MyField");
            // want to add custom state to the error here
            break;
    }
});

Background: I apply my validation to hundreds of items, so having a custom state indicating on which of these items the validation failed would be quite useful.

Answer 1

Got it, one needs to manually create the ValidationFailure:

var failure = new ValidationFailure
{
    ErrorMessage = "Unexpected value for ...",
    CustomState = "your custom state"
};
context.AddFailure(failure);