FluentValidation - Check value is a date only if NOT NULL

Question

I have a bool along with a nullable DateTime property. The DateTime is only required if the bool is set to true... And I want to validate the date if the bool is true.

I have this expression so far...

When(p => p.HasVisa == true, () => RuleFor(p => p.VisaExpiryDate).NotNull());

Now I try to validate the date in that expression using the .Must extension and my custom BeAValidDate method...

When(p => p.HasVisa == true, () => RuleFor(p => p.VisaExpiryDate).NotNull().Must(BeAValidDate));

private bool BeAValidDate(DateTime date)
{
  if (date == default(DateTime))
    return false;
  return true;
}

But the .Must extension doesn't allow me to operate on a DateTime that is nullable. How do I do this sort of validation on a nullable date?

I've never used FluentValidation, but isn't your problem just that your `BeAValidDate` does not take `DateTime?` (ie a nullable DateTime) as a parameter? — Joachim Isaksson, May 25 '13 at 06:50
LOL thanks Joachim, I was overthinking the whole thing, yes you are correct. — Greg Quinn, May 25 '13 at 07:10

score 30 · Answer 1 · edited Mar 12 '19 at 19:21

30

Just add ‘When’ to check if the object is not null:

RuleFor(x => x.AlternateNumber)
    .Must(IsAllDigits)
    .When(x => !string.IsNullOrEmpty(x.AlternateNumber))
    .WithMessage("AlternateNumber should contain only digits");

edited Mar 12 '19 at 19:21

gunr2171

16,104
25
61
88

answered Aug 25 '16 at 13:15

Sagar Nanivadekar

421
4
3

1

I know this is not the case, but for those cases in which you have more rules to set, you can use the DependentRules method – ndarriulat Aug 27 '19 at 14:14

score 3 · Accepted Answer · answered May 25 '13 at 07:15

As Joachim mentioned I need to have overloads for BeAValidDate that accepts both null and non-null dates.

private bool BeAValidDate(DateTime date)
{
  if (date == default(DateTime))
    return false;
  return true;
}

private bool BeAValidDate(DateTime? date)
{
  if (date == default(DateTime))
    return false;
  return true;
}

score 2 · Answer 3 · edited Dec 09 '19 at 13:28

2

This work for me:

RuleFor(user => user.DateOfBirth)
  .Must(p=> !(p == DateTime.MinValue))
  .WithMessage("DateTime not null");

edited Dec 09 '19 at 13:28

FortyTwo

2,414
3
22
33

answered Oct 09 '19 at 15:13

Luis Miguel Burdier

21
2

FluentValidation - Check value is a date only if NOT NULL

3 Answers3