12.0 Upgrade Guide

Introduction

FluentValidation 12.0 is a major release that included several breaking changes. Please review this document carefully before upgrading from FluentValidation 11.x to 12.

The main goal of this release was removal of deprecated code and removal of support for obsolete platforms. There are no new features in this release.

Changes in supported platforms

Support for the following platforms has been removed:

• .NET Core 3.1 (Microsoft’s support ended in December 2022)
• .NET 5 (Microsoft’s support ended in November 2022)
• .NET 6 (Microsoft’s support ended in November 2024)
• .NET 7 (Microsoft’s support ended in November 2024)
• .NET Standard 2.0/2.1

.NET 8 is now the minimum supported version.

If you still need .NET Standard 2.0 compatibility then you will need to continue to use FluentValidation 11.x and only upgrade to FluentValidation 12 once you’ve moved to a more modern version of .NET.

Removal of the Transform and TransformForEach methods

The Transform and TransformForEach methods deprecated in 11.x have been removed. For details on how to migrate see https://github.com/FluentValidation/FluentValidation/issues/2072

Removal of CascadeMode.StopOnFirstFailure

The StopOnFirstFailure cascade option was deprecated in FluentValidation 11.0 and has now been removed, along with the AbstractValidator.CascadeMode and ValidatorOptions.Global.CascadeMode properties which were also deprecated in 11.0.

If were previously setting ValidatorOptions.Global.CascadeMode to Continue or Stop, you can simply replace this with the following:

ValidatorOptions.Global.DefaultClassLevelCascadeMode = CascadeMode.<YourCurrentValue>;
ValidatorOptions.Global.DefaultRuleLevelCascadeMode = CascadeMode.<YourCurrentValue>;

If you were previously setting it to StopOnFirstFailure, replace it with the following:

ValidatorOptions.Global.DefaultRuleLevelCascadeMode = CascadeMode.Stop;

Similarly, if you were previously setting AbstractValidator.CascadeMode to Continue or Stop, replace this with the following:

ClassLevelCascadeMode = CascadeMode.<YourCurrentValue>;
RuleLevelCascadeMode = CascadeMode.<YourCurrentValue>;

If you were previously setting it to StopOnFirstFailure, replace it with the following:

ClassLevelCascadeMode = CascadeMode.Continue;
RuleLevelCascadeMode = CascadeMode.Stop;

If you were calling .Cascade(CascadeMode.StopOnFirstFailure) in a rule chain, replace StopOnFirstFailure with Stop.

Removal of InjectValidator and related methods

The InjectValidator method was deprecated in 11.x and removed in 12.0.

This method allowed you to implicitly inject a child validator from the ASP.NET Service Provider:

public class PersonValidator : AbstractValidator<Person> 
{
  public PersonValidator() 
  {
    RuleFor(x => x.Address).InjectValidator();
  }
}

Assuming that the address property is of type Address, the above code would attempt to resolve an IValidator<Address> and use this to validator the Address property. This method can only be used when working with ASP.NET MVC’s auto-validation feature and cannot be used in other contexts.

Instead of using InjectValidator, you should instead use a more traditional constructor injection approach, which is not just limited to ASP.NET MVC:

public class PersonValidator : AbstractValidator<Person> 
{
  public PersonValidator(IValidator<Address> addressValidator) 
  {
    RuleFor(x => x.Address).SetValidator(addressValidator);
  }
}

Removal of AbstractValidator.EnsureInstanceNotNull

In previous versions of FluentValidation it was possible to override the AbstractValidator.EnsureInstanceNotNull method to disable FluentValidation’s root-model null check. The ability to do this was deprecated in 11.5.x and has now been removed. For further details please see https://github.com/FluentValidation/FluentValidation/issues/2069

Changes to the Serbian language translations

The existing Serbian translations have been renamed to Serbian (Latin) and are now available under the sr-Latn language code. A new Serbian (Cyrillic) language has been added, which is now the default for the sr language code.

Other breaking API changes

• The ITestValidationContinuation interface now exposes a MatchedFailures property (as well as the existing UnmatchedFailures)
• The ShouldHaveAnyValidationError method has been renamed to ShouldHaveValidationErrors
• ShouldNotHaveAnyValidationErrors and ShouldHaveValidationErrors are now instance methods on TestValidationResult, instead of extension methods.