How to force IRuleBuilder in AbstractValidator to act as 'if' statement?

Question

This is my code:

RuleFor(x => x.Content).NotEmpty().Must(content => content.Trim().Length > 0);

I expect it should behave as

if (NotEmpty(x.Content) && x.Content.Trim().Length > 0)

statement but it throws NullReferenceException if x.Content is null.

Please help me with a workaround.

Show your full code.. You can read [What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net) — Soner Gönül, Mar 15 '13 at 09:57
well I guess `NotEmpty(x.Content)` will also throw an exception if `x.Content == null` so you will ne to check for that — DerApe, Mar 15 '13 at 10:07

score 2 · Answer 1 · answered Mar 15 '13 at 10:08

There is Unless which allows you to execute a rule based on a condition. You need to split up your rule into two, however:

RuleFor(x => x.Content).NotEmpty();
RuleFor(x => x.Content).Must(content => content.Trim().Length > 0).Unless(x => x == null);

Or you could use the ?? operator, which is even more compact:

RuleFor(x => (x.Content ?? "").Trim()).NotEmpty();

score 2 · Accepted Answer · answered Mar 25 '13 at 16:15

2

It seems this code works perfectly too:

RuleFor(x => x.Content)   
    .Cascade(CascadeMode.StopOnFirstFailure)    
        .NotEmpty()   
        .Must(content => content.Trim().Length > 0);

answered Mar 25 '13 at 16:15

SKINDER

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score 1 · Answer 3 · answered Mar 15 '13 at 10:07

You could write a custom rule. If the rule returns true, then create a ValidationFailure. Something like this:

public class ViewModelValidator : AbstractValidator<ViewModel>
{
    public ViewModelValidator()
    {
        Custom(r => ContentIsEmpty(r) ? new ValidationFailure("Content", "Content must not be empty.") : null);
    }

    private static bool ContentIsEmpty(ViewModel viewModel)
    {
        return string.IsNullOrWhiteSpace(viewModel.Content);
    }
}

How to force IRuleBuilder in AbstractValidator to act as 'if' statement?

3 Answers3