Disable auto-validation

FV works just like ASP.NET’s own validation - before an action is executed, it automatically validates the arguments, and populates the ModelState. So in the action you can check ModelState.IsValid and everything “just works”.

Is it possible to disable this auto-validation, and only run it on demand?

We use a CQRS pipeline (using MediatR), which performs validation. A typical validator and action:

// the validator
public class CommandValidator : AbstractValidator<Command> { ... }

// the action
public IActionResult Edit(Command command)
{
    // note there is no check for ModelState.IsValid
    _mediator.Send(command);
    return View();
}

So, FV performs auto-validation for that action, and the CQRS pipeline thereafter also performs validation - so the input is validated twice, and the UI shows two validation errors for every invalid property.

Is it possible to configure FV to only validate on demand, and not automatically before every action?

[julianpaulozzi]

It’s nice to have automatic validation for everything in simple configuration entry. But can not ignore some edge cases with an attribute or interface for example?

[JeremySkinner]

That’s handled by the FluentValidationClientModelValidatorProvider, which is all set up through the AddFluentValidation() method. If you’re not using the automatic integration, you’ll need to register all that manually (and also create your own ViewOptionsSetup class to plug it into MVC). I’d suggest looking through the code of the FluentValidationMvcExtensions class (https://github.com/JeremySkinner/FluentValidation/blob/master/src/FluentValidation.AspNetCore/FluentValidationMvcExtensions.cs), particularly lines 61-67 and 120-127. That should give you everything you need.