Child Model Validation using Parent Model Values. Fluent Validation. MVC4

Question

Below is a simplified version of my problem.

I can not flatten the model. There is a List of "children" that I need to validate a birthday.

I can not seem to reference the date in the Parent class and was wondering how this is done in Fluent Validation?

Model

[Validator(typeof(ParentValidator))]
public class Parent
{
    public string Name { get; set; }
    public DateTime Birthdate { get; set; }

    public List<Child> Children { get; set; }
}

public class Child
{
    public string ChildProperty{ get; set; }
    public DateTime Birthdate { get; set; }
}

Validator

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
         RuleFor(model => model.Name).NotEmpty();
         RuleForEach(model => model.Children).SetValidator(new ChildValidator());
    }
}

public class ChildValidator : AbstractValidator<Child>
{
    public ChildValidator()
    {
        RuleFor(model => model.ChildProperty).NotEmpty();
        //Compare birthday to make sure date is < Parents birthday
    }
}

johnny 5 · Accepted Answer · 2021-01-26 15:31:27Z

36

Edit: SetCollectionValidator has been deprecated, however the same can be done now using RuleForEach:

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
         this.RuleFor(model => model.Name).NotEmpty();
         this.RuleForEach(model => model.Children)
                .SetValidator(model => new ChildValidator(model));
    }
}

public class ChildValidator : AbstractValidator<Child>
{
    public ChildValidator(Parent parent)
    {
        this.RuleFor(model => model.ChildProperty).NotEmpty();
        this.RuleFor(model => model.Birthday).Must(birthday => parent.Birthday < birthday);
    }
}

edited Jan 26, 2021 at 15:31

answered Feb 3, 2016 at 20:40

johnny 5

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11 Comments

Tommy Grovnes Over a year ago

How are you comparing the birthdays ? I don't understand your answer ?

johnny 5 Over a year ago

The important part of this Question is how to do Child validation. I'm not comparing birthdays that comment is for you to add the birthday logic rules there

Tommy Grovnes Over a year ago

The question is about how to compare the child's birthday to the parent's, it is not obvious from your example how that can be accomplished, adding the comparison would make it a better answer. quotes: "I need to validate a birthday." "I can not seem to reference the date in the Parent class and was wondering how this is done in Fluent Validation?"

johnny 5 Over a year ago

Your right something looks wierd here, was this question updated in the past give me a second I'll update this

johnny 5 Over a year ago

@TommyGrovnes Idk what happened there but its fixed now

|

Tommy Grovnes · Accepted Answer · 2013-09-11 13:25:40Z

30

Create a custom property validator like this

public class AllChildBirtdaysMustBeLaterThanParent : PropertyValidator
{
    public AllChildBirtdaysMustBeLaterThanParent()
        : base("Property {PropertyName} contains children born before their parent!")
    {
    }

    protected override bool IsValid(PropertyValidatorContext context)
    {
        var parent = context.ParentContext.InstanceToValidate as Parent;
        var list = context.PropertyValue as IList<Child>;

        if (list != null)
        {
            return ! (list.Any(c => parent.BirthDay > c.BirthDay));
        }

        return true;
    }
}

Add rules like this

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
        RuleFor(model => model.Name).NotEmpty();
        RuleFor(model => model.Children)
               .SetValidator(new AllChildBirtdaysMustBeLaterThanParent());

        // Collection validator
        RuleFor(model => model.Children).SetCollectionValidator(new ChildValidator());
    }
}

Alternative to the Custom Property validator is to use the Custom method:

    public ParentValidator()
    {
        RuleFor(model => model.Name).NotEmpty();
        RuleFor(model => model.Children).SetCollectionValidator(new ChildValidator());

        Custom(parent =>
        {
            if (parent.Children == null)
                return null;

            return parent.Children.Any(c => parent.BirthDay > c.BirthDay)
               ? new ValidationFailure("Children", "Child cannot be older than parent.")
               : null;
        });
    }

Crude way of showing indicies that failed: (should probably be name of some other identifier)

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
        RuleFor(m => m.Children).SetCollectionValidator(new ChildValidator());

        Custom(parent =>
        {
            if (parent.Children == null)
                return null;

            var failIdx = parent.Children.Where(c => parent.BirthDay > c.BirthDay).Select(c => parent.Children.IndexOf(c));
            var failList = string.Join(",", failIdx);

            return failIdx.Count() > 0
               ? new ValidationFailure("Children", "Child cannot be older than parent. Fail on indicies " + failList)
               : null;
        });
    }

}

edited Sep 11, 2013 at 13:25

answered Sep 10, 2013 at 13:35

Tommy Grovnes

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9 Comments

Dustin Harrell Over a year ago

I am working with this. Currently my issue is that when I make this change my partial view starts griping about "No parameterless constructor defined for this object." And it was working before hand.

Dustin Harrell Over a year ago

Actually a more concise error I found is that RuleForEach(model => model.Children) .SetValidator(new ChildValidator(model)); I can not pass model in the .SetValidator. The message is "The name "model" does not exist in this current context"

Tommy Grovnes Over a year ago

As far as I can see, this is the cleanest approach for now

Dustin Harrell Over a year ago

Is there another approach because this one wont even compile because model has no value in the context?

Tommy Grovnes Over a year ago

Updated my answer with an example for the Custom method approach, would you +1 the answer ?

|

Kristoffer Jälén · Accepted Answer · 2017-11-16 10:09:47Z

14

Nowadays the answer by @johnny-5 can be simplified even further by using the SetCollectionValidator extension method and passing the parent object to the child validator:

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
         RuleFor(model => model.Name).NotEmpty();
         RuleFor(model => model.Children)
             .SetCollectionValidator(model => new ChildValidator(model))
    }
}

public class ChildValidator : AbstractValidator<Child>
{
    public ChildValidator(Parent parent)
    {
        RuleFor(model => model.ChildProperty).NotEmpty();
        RuleFor(model => model.Birthday).Must(birthday => parent.Birthday < birthday);
    }
}

answered Nov 16, 2017 at 10:09

Kristoffer Jälén

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2 Comments

Paul Suart Over a year ago

@johnny 5's answer passes the parent validator to the child validator; yours passes the parent model to the child validator.

Nugsson Over a year ago

SetCollectionValidator is deprecated - see docs.fluentvalidation.net/en/latest/upgrading-to-8.html. "SetCollectionValidator was added to FluentValidation in its initial versions to provide a way to use a child validator against each element in a collection. RuleForEach was added later and provides a more comprehensive way of validating collections (as you can define in-line rules with RuleForEach too). It doesn’t make sense to provide 2 ways to do the same thing."

Badgerspot · Accepted Answer · 2019-10-31 12:22:12Z

9

Building on the answer of @kristoffer-jalen it is now:

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
         RuleFor(model => model.Name).NotEmpty();
         //RuleFor(model => model.Children)
         //    .SetCollectionValidator(model => new ChildValidator(model))
         RuleForEach(model => model.Children)
                .SetValidator(model => new ChildValidator(model));
    }
}

public class ChildValidator : AbstractValidator<Child>
{
    public ChildValidator(Parent parent)
    {
        RuleFor(model => model.ChildProperty).NotEmpty();
        RuleFor(model => model.Birthday).Must(birthday => parent.Birthday < birthday);
    }
}

as SetCollectionValidator is deprecated.

answered Oct 31, 2019 at 12:22

Badgerspot

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1 Comment

thanzeel Over a year ago

i tried this, at runtime, the SetValidator method is trying to look for an instance of the model from the DI and i get exception that the DI has no such object instance. any idea baout it?

Drury Lumenta · Accepted Answer · 2022-09-23 04:01:58Z

1

Pass the parent to custom logic with .Must(), then do the validation manually.

public class ParentValidator : AbstractValidator<Parent>
{
    public ParentValidator()
    {
         RuleFor(model => model.Name).NotEmpty();
         RuleFor(model => model).Must(BeValidBirtDate).WithMessage("BirthDate Invalid");
    }

    public bool BeValidBirtDate(Parent parent)
    {
        foreach(var child in parent.Children)
        {
            if (DateTime.Compare(child.BirthDate, parent.BirthDate) == -1)
                return false;
        }
        return true;
    }
}

answered Sep 23, 2022 at 4:01

Drury Lumenta

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