The validator does not work with collection arguments

Consider this validator

    public class FooValidator : AbstractValidator<Foo>
    {
        public FooValidator()
        {
            RuleFor(foo => foo.Bar)
                .NotEmpty()
                .NotNull();
        }
    }

And this action method

        [HttpPost]
        public Task Foobar([FromBody]IEnumerable<Foo> foo)
        {


            
        }

The library fails to validate

[JeremySkinner]

Actually that functionality is already in place but not released yet. Coming in 8.2. You’ll be able to retrieve the service provider from the context (in asp.net core projects), and there are some shortcut methods for retrieving validators.

Regarding singletons: yes there is a performance benefit from caching, but it’s not huge. The expensive part is compiling the rule lambda expressions to delegates, but we already perform separate caching for this. You can of course register validators as singleton if you prefer, but I found that back when this used to be the default it created a huge amount of confusion for developers who didn’t understand the implications of dependency lifetimes, so defaulting to transient is the path of least resistance.

[AndersMalmgren]

Yes validators are registered as transient by default to avoid the pitfalls that come with trying to inject dependencies into Singleton-scoped validators.

I’d inject the IAccountValidator directly though, rather than the service provider.

Downside is you need to run your rule mapping everytime. A singleton could have been cached. Probably not a problem for our models though. Yes, I ment that with “Ah it seems the validator is registered transient, so I can use constructor injection.”. Since its a transient scope I can use constrtor injection instead of service locator pattern. Though a custom locator pattern for the context would have been pretty ok. Then you can benefit from singleton caching of the rules. Like

    public class InvoiceValidator : AbstractValidator<Invoice>
    {
        public InvoiceValidator()
        {
            RuleFor(invoice => invoice.ToAccount)
                .Custom((account, ctx) =>
                {
                    if(!ctx.GetService<IAccountValidator>().Validate(account))
                        ctx.AddFailure("Receiving bank account is not valid");
                });
        }
    }