Fluent validation and Must custom validation

Question

I have a class and my validation looks like this:

    public ValidationResult Validate(CustomerType customerType)
    {
        CustomerType Validator validator = new CustomerTypeValidator();
        validator.RuleFor(x => x.Number).Must(BeUniqueNumber);

        return validator.Validate(customerType);
    }

    public bool BeUniqueNumber(int number)
    {
        //var result = repository.Get(x => x.Number == customerType.Number)
        //                       .Where(x => x.Id != customerType.Id)
        //                       .FirstOrDefault();

        //return result == null;
        return true;
    }

The CustomerTypeValidator is a basic validator class that validates string properties.

I also add a new rule to check if the number is unique in the db. I do it in this class because there's a reference to the repository. The validator class has no such reference.

The problem here is that the BeUniqueNumber method should have a CustomerType parameter. However when I do this, I get an error on the RuleFor line above because 'Must' needs an int as a parameter.

Is there a way around this?

danludwig · Accepted Answer · 2014-11-05 13:20:26Z

3

Can you try this?

public ValidationResult Validate(CustomerType customerType)
{
    CustomerTypeValidator validator = new CustomerTypeValidator();
    validator.RuleFor(x => x).Must(HaveUniqueNumber);

    return validator.Validate(customerType);
}

public bool HaveUniqueNumber(CustomerType customerType)
{
    var result = repository.Get(x => x.Number == customerType.Number)
        .Where(x => x.Id != customerType.Id)
        .FirstOrDefault();

    return result == null;
    //return true;
}

You should also be able to do this:

public ValidationResult Validate(CustomerType customerType)
{
    CustomerTypeValidator validator = new CustomerTypeValidator();
    validator.RuleFor(x => x.Number).Must(BeUniqueNumber);

    return validator.Validate(customerType);
}

public bool BeUniqueNumber(CustomerType customerType, int number)
{
    var result = repository.Get(x => x.Number == number)
        .Where(x => x.Id != customerType.Id)
        .FirstOrDefault();

    return result == null;
    //return true;
}

"I also add a new rule to check if the number is unique in the db. I do it in this class because there's a reference to the repository."

Well, why can't you give your validator a reference to the repository too?

CustomerTypeValidator validator = new CustomerTypeValidator(repository);

edited Nov 5, 2014 at 13:20

answered Nov 5, 2014 at 13:11

danludwig

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6 Comments

Ivan-Mark Debono Over a year ago

I tried that too. It doesn't work because 'Must' needs <T, TProperty>

danludwig Over a year ago

@Ivan-MarkDebono that's odd, are you sure? I just tried something very similar, and the Predicate method only needs a T, not a TProperty. Are you sure you are doing x => x, and not x => x.Number? I have also updated my answer with another alternative.

Ivan-Mark Debono Over a year ago

I've already tried both ways and they won't work. I'd rather not pass the repository around if there's a solution without doing so.

danludwig Over a year ago

@Ivan-MarkDebono what version of fluent validation are you using? Are you getting a compiler / build error? If so, what is the exact error? Like I said, the above code works when I build it (against FluentValidation 5.0.0.1). Could you provide the source for your CustomerType and CustomerTypeValidator in the OP?

Ivan-Mark Debono Over a year ago

My bad. Your answer with the first example works fine. I had BeUniqueNumber() when I re-edited the code.

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