FluentValidation 子验证器中的 PropertyName

Question

I'm trying something a little odd in FluentValidation and I can't quite seem to make it work. The model I'm validating has strings in it and I would like run validations on the objects they parse to, for example, that a date serialized as a string is before right now, like so:

RuleFor(x => x.SentDateString).AsDate(d => d.DateInPast());

I recognize that the normal way to do that is make the model itself contain the parsed dates and other objects and then validate the deserialized data, but I have my reasons for wanting to do it this way.

I have this working like this:

// general mechanism for adding "casting" rules
public static IRuleBuilderOptions<T, TFrom> Xform<T, TFrom, TTo>(
    this IRuleBuilder<T, TFrom> ruleBuilder,
     Func<TFrom, TTo> xform,
     Func<IRuleBuilder<TFrom, TTo>, IRuleBuilderOptions<TFrom, TTo>> innerRules)
{
    var innerValidator = new InlineValidator<TFrom>() {
        v => innerRules(v.RuleFor(x => xform(x)))
    };
    return ruleBuilder.SetValidator(innerValidator);
}

// specific rule for making a date
public static IRuleBuilder<T, string> AsDate<T>(
    this IRuleBuilder<T, string> ruleBuilder,
    Func<IRuleBuilder<string, DateTime>, IRuleBuilderOptions<string, DateTime>> innerRules)
{
    Func<string, DateTime> parseDate = (s) =>
    {
        DateTime d;
        DateTime.TryParse(s, CultureInfo.InvariantCulture, DateTimeStyles.RoundtripKind, out d);
        return d;
    };
    return Xform(ruleBuilder, parseDate, innerRules);
}

// inner rule used in validating the date object
public static IRuleBuilderOptions<T, DateTime> DateInPast<T>(this IRuleBuilder<T, DateTime> ruleBuilder) =>
    ruleBuilder.LessThan(DateTime.Now.Add(TimeSpan.FromMinutes(5)))
        .WithMessage("{PropertyName} must be in the past");

This does validate the property! However, the property name doesn't transfer through to the child validator, so I get messages like:

  must be in the past

Where I expected "SentDateString" at the front of that. I haven't been able to figure out how to make that work. Is there an easy way? Am I doing the whole thing wrong?

Answer 1

This turned out to be pretty easy, just needed to pass in an IRuleBuilderOptions instead of an IRuleBuilder and then use Configure to copy over the display name.

public static IRuleBuilderOptions<T, TFrom> Xform<T, TFrom, TTo>(
    this IRuleBuilderOptions<T, TFrom> ruleBuilder,
    Func<TFrom, TTo> xform,
    Func<IRuleBuilder<TFrom, TTo>, IRuleBuilderOptions<TFrom, TTo>> innerRules)
{
    var innerValidator = new InlineValidator<TFrom>() {
        v => innerRules(v.RuleFor(x => xform(x)))
                .Configure(c1 => ruleBuilder.Configure(c2 => c1.DisplayName = c2.DisplayName))
    };
    return ruleBuilder.SetValidator(innerValidator);
}