FluentValidation 9 ChildValidatorAdaptor Upgrade guide

FluentValidation 9 NET Core 3.1

I can’t get new ChildValidatorAdaptor working. Can you provide more details on how to use those generic parameters? My old method:

This is code from version 8 which works:

public class PolymorphicValidator<TInterface> : ChildValidatorAdaptor
{
    readonly Dictionary<Type, IValidator> _derivedValidators = new Dictionary<Type, IValidator>();

    // Need the base constructor call, even though we're just passing null.
    public PolymorphicValidator() : base((IValidator)null, typeof(IValidator<TInterface>))
    {
    }

    public PolymorphicValidator<TInterface> Add<TDerived>(IValidator<TDerived> derivedValidator) where TDerived : TInterface
    {
        _derivedValidators[typeof(TDerived)] = derivedValidator;
        return this;
    }

    public override IValidator GetValidator(PropertyValidatorContext context)
    {
        // bail out if the current item is null 
        if (context.PropertyValue == null) return null;

        if (_derivedValidators.TryGetValue(context.PropertyValue.GetType(), out var derivedValidator))
        {
            return derivedValidator;
        }

        return null;
    }
}

`

[wast]

It works. Thank you!

[JeremySkinner]

That implementation I linked to definitely doesn’t work, here’s an updated version that handles the type conversion correctly:

public class PolymorphicValidator<T, TInterface> : ChildValidatorAdaptor<T, TInterface>
{
	readonly Dictionary<Type, IValidator> _derivedValidators = new Dictionary<Type, IValidator>();

	// Need the base constructor call, even though we're just passing null.
	public PolymorphicValidator() : base((IValidator<TInterface>)null, typeof(IValidator<TInterface>))
	{
	}

	public PolymorphicValidator<T, TInterface> Add<TDerived>(IValidator<TDerived> derivedValidator) where TDerived : TInterface {
		_derivedValidators[typeof(TDerived)] = derivedValidator;
		return this;
	}

	public override IValidator<TInterface> GetValidator(PropertyValidatorContext context)
	{
		// bail out if the current item is null
		if (context.PropertyValue == null) return null;

		if (_derivedValidators.TryGetValue(context.PropertyValue.GetType(), out var derivedValidator)) {
			return new ValidatorWrapper(derivedValidator);
		}

		return null;
	}

	private class ValidatorWrapper : AbstractValidator<TInterface> {

		private IValidator _innerValidator;
		public ValidatorWrapper(IValidator innerValidator) {
			_innerValidator = innerValidator;
		}

		public override ValidationResult Validate(ValidationContext<TInterface> context) {
			return _innerValidator.Validate(context);
		}

		public override Task<ValidationResult> ValidateAsync(ValidationContext<TInterface> context, CancellationToken cancellation = new CancellationToken()) {
			return _innerValidator.ValidateAsync(context, cancellation);
		}

		public override IValidatorDescriptor CreateDescriptor() {
			return _innerValidator.CreateDescriptor();
		}
	}
}

We’ll probably come up with a slightly better solution for when this is properly added to the library, but this should work for now.

Could you give that a try and let me know if it works ok?