FluentValidation Set Valid Result to a Custom Property

Question

I am validating the content for file import and I have an IsValid property for each line.

public class Header 
{
    public int LineNumber { get; set; }
    public string Property1 { get; set; }
    public string Property2 { get; set; }
    public bool IsValid { get; set; }
}

public class Detail
{
    public int LineNumber { get; set; }
    public string Property1 { get; set; }
    public string Property2 { get; set; }
    public string Property3 { get; set; }
    public bool IsValid { get; set; }
}

public class Trailer
{
    public int LineNumber { get; set; }
    public string Property1 { get; set; }
    public bool IsValid { get; set; }
}

public class ImportFile
{
    public Header Header { get; set; }
    public List<Detail> Details { get; set; }
    public Trailer Trailer { get; set; }
}

and my validators look somewhat like:

public class DetailValidator : AbstractValidator<Detail>
{
    public DetailValidator()
    {
        RuleFor(d => d.Property1)
            .Cascade(CascadeMode.Stop)
            .NotEmpty()
            .WithState(d => d.LineNumber)
            .Length(3)
            .WithState(d => d.LineNumber);

        RuleFor(d => d.Property2)
            .Cascade(CascadeMode.Stop)
            .NotEmpty()
            .WithState(d => d.LineNumber)
            .MaximumLength(50)
            .WithState(d => d.LineNumber);

        ...
    }
}

public class ImportFileValidator : AbstractValidator<ImportFile>
{
    public ImportFileValidator()
    {
        RuleFor(f => f.Header)
            .SetValidator(new HeaderValidator());

        RuleForEach(f => f.Details)
            .SetValidator(new DetailsValidator());

        ...
    }   
}

After I call the validation, I wanted to set the IsValid property of each line of the file (be it header, detail or trailer) base from the result of the validation.

What is possible for now is, since I am using WithState to store the LineNumber, I can match the ValidationResult against the ImportFile instance to set each line's validity like below:

ImportFile file = // parsed file content
var result = new ImportFileValidator().Validate(file);

foreach (var detail in file.Details)
{
    var error = result.Errors.FirstOrDefault(e => 
        Convert.ToInt32(e.CustomState) == detail.LineNumber);

    detail.IsValid = error == null;
}

And I have to check for the header and trailer as well.

Is there a way I can do this inside the validators? I am trying to explore the FluentValidation's documentation, but I can't seem to find what I needed there.

Answer 1

As I was exploring the available methods in FluentValidation, I saw OnFailure and OnAnyFailure methods. This methods might be a good help to what I needed to do, but the problem is they're obsolete as of 10.3.0 and will be removed on version 11. They're suggesting to use a custom validator instead.

1. The Header, Detail and Trailer Abstract Validators remain as is.

2. I created custom validator extensions for those 3.

Each extension methods creates an instance of the corresponding validator and executes it. I can make them generic for header, detail and trailer since they will do the same thing, set IsValid property to the validation result.

public static IRuleBuilderOptionsConditions<ImportFile, T> IsHeaderValid<T>(this IRuleBuilder<ImportFile, T> ruleBuilder)
    where T : Header
{
    return builder.Custom((header, context) =>
    {
        // Create the Header Abstract Validator Instance
        var validator = new HeaderValidator();
        var result = validator.Validate(Header);

        header.IsValid = result.IsValid;

        // Pass the errors to the context
        result.Errors.ForEach(context.AddFailure);
    }
}

3. I had to change the ImportFileValidator to call the custom validators, instead of using setvalidator.

The ImportFileValidator looks like this:

public class ImportFileValidator : AbstractValidator<ImportFile>
{
    public ImportFileValidator()
    {
        RuleFor(f => f.Header)
            .IsHeaderValid();

        RuleForEach(f => f.Details)
            .IsDetailValid();

        ...
    }   
}

This is pretty much how I was able to set the IsValid property without having to do the matching I initially did in the question.