Client-side validation not working

I have a validator that is working correctly but I haven’t yet been able to get the respective client-side validation to work.

    FluentValidationModelValidatorProvider.Configure(provider => 
            {
                provider.ValidatorFactory = new BrandValidationFactory();
                provider.Add(
                            typeof(RequiredIfStatusIsEmployedOrSelfEmployedValidator),
                            (metadata, context, rule, validator) => new RequiredIfStatusIsEmployedOrSelfEmployedClientValidator(metadata, context, rule, validator));
            });

RequiredIfStatusIsEmployedOrSelfEmployedValidator inherits PropertyValidator and overrides the protected method:

protected override bool IsValid(PropertyValidatorContext context)
        {
            if (!EmployedStatuses.Contains(applicationFormContext.Application.MainApplicant.EmploymentStatusId.ToUnderlyingType().ToString(CultureInfo.InvariantCulture)))
            {
                return true;
            }

            return context.PropertyValue != null && !IsInvalidString(context.PropertyValue);
        }

RequiredIfStatusIsEmployedOrSelfEmployedClientValidator inherits FluentValidationPropertyValidator and overrides the public method:

public override IEnumerable<ModelClientValidationRule> GetClientValidationRules()
        {
            yield return new ModelClientValidationMinLengthRule("testError1", 100);
        }

Finally, the configure method:

FluentValidationModelValidatorProvider.Configure(provider => 
            {
                provider.ValidatorFactory = new BrandValidationFactory();
                provider.Add(
                            typeof(RequiredIfStatusIsEmployedOrSelfEmployedValidator),
                            (metadata, context, rule, validator) => new RequiredIfStatusIsEmployedOrSelfEmployedClientValidator(metadata, context, rule, validator));
            });

The client validator never gets called and, therefore, the data- attributes never get rendered on the HTML.

What am I missing?

[JeremySkinner]

Yes you must always provide a string source used to generate the message. The recommended approach is to define the “default” message in the custom property validator’s constructor (this is how FV’s default validators all work), which you can then override using WithMessage if needed.

[fabiomilheiro]

Well, I found out. My property validator constructor calls the base constructor with a null string source which is set here:

    protected PropertyValidator(IStringSource errorMessageSource)
    {
      this.originalErrorSource = this.errorSource = errorMessageSource;
    }

The field errorSource is used in the last line of the BuildErrorMessage method:

    private string BuildErrorMessage(PropertyValidatorContext context)
    {
      if (this.customFormatArgs != null && this.customFormatArgs.Count > 0)
      {
        object[] array = this.customFormatArgs.Select<Func<object, object, object>, object>((Func<Func<object, object, object>, object>) (func => func(context.Instance, context.PropertyValue))).ToArray<object>();
        context.MessageFormatter.AppendAdditionalArguments(array);
      }
      object context1 = this.errorSource is IContextAwareStringSource ? (object) context : context.Instance;
      return context.MessageFormatter.BuildMessage(this.errorSource.GetString(context1));
    }

To fix this I could pass a not null error source but I decided to add the message fluently which ends up setting that value too as a StaticStringSource:

    RuleFor(x => x.EmploymentSectorId)
                .SetValidator(new RequiredIfStatusIsEmployedOrSelfEmployedValidator(applicationFormContext))
                .WithName(fields.EmploymentSector.Label)
                .WithMessage("The {PropertyName} is not valid.");

Thanks for your help @JeremySkinner!