Question

Using FluentValidation, is it possible to throw an exception on a single rule failure? For example, I would like to call Validate() and for the first rule below to simply validate but the second to throw an exception if false.

RuleFor(x => x.Title)
    .NotEmpty()
    .WithMessage("Please add a title for the project");

RuleFor(x => x.UserId)
    .NotEmpty()
    .WithMessage("User not supplied");

I’m probably trying to force FluentValidation to do something it is not designed to do. And I am aware of the ValidateAndThrow() method, but this will throw an exception on any failure.

Answer 1

Yes. Try something along these lines –

Add FluentValidation and FluentValidation.TestHelper to your directives.

    private readonly IValidator<ItemViewModel> validator = new ItemValidator(); 
    //Assumes your fluent validation is in ItemValidator and your view model is ItemViewModel

    [Test]
    public void Headline_ShouldNotBeEmpty()
    {
        validator.ShouldHaveValidationErrorFor(f => f.message, string.Empty);
    }