CODEWITHSUNDEEP
c#asp.net-corefluentvalidation
Ryan Buening
Ryan Buening

Reputation: 1660

FluentValidation NullReferenceException - Way to prevent checking for null values?

If I have something like this:

When(x => x.SendMail.Equals("Y"), () =>
{
    RuleFor(x => x.To).NotEmpty();
    RuleFor(x => x.From).NotEmpty();
    RuleFor(x => x.EmailAddress).NotEmpty();
});

and SendMail does not have a value, I will get a NullReferenceException. However, if I surround the When() like so:

When(x => x.SendMail != null, () =>
{
    When(x => x.SendMail.Equals("Y"), () =>
    {
        RuleFor(x => x.To).NotEmpty();
        RuleFor(x => x.From).NotEmpty();
        RuleFor(x => x.EmailAddress).NotEmpty();
    });
});

it works as I would expect and I do not get a NRE when SendMail does not have a value. I'm new to FluentValidaton and C# in general. Is this the proper way to go about handling validations like this? Do I need to wrap all logic like this with null checks?

Upvotes: 2

Views: 3396

Answers (4)

Igor
Igor

Reputation: 62213

The easiest thing to do is just switch the comparison.

When(x => x.SendMail.Equals("Y"), () => // etc

becomes

When(x => "Y".Equals(x.SendMail), () => // etc

This works because "Y" is never null (so the Equals method can be called which is where your current code fails) and will also not throw an NRE when doing a comparison inside of the Equals method as a null value will simply return false.

Upvotes: 4

dawid
dawid

Reputation: 29

@Ryan Buening you are trying to call instance method of null object so you are getting NullReferenceException and this is normal for c#. I think you could use null conditional operator from c#6

When(x => x.SendMail?.Equals("Y"), () =>
{
    RuleFor(x => x.To).NotEmpty();
    RuleFor(x => x.From).NotEmpty();
    RuleFor(x => x.EmailAddress).NotEmpty();
});

Upvotes: 0

Nkosi
Nkosi

Reputation: 247133

What you are doing can be simplified to 

When(x => x.SendMail != null && x.SendMail.Equals("Y"), () =>
{
    RuleFor(x => x.To).NotEmpty();
    RuleFor(x => x.From).NotEmpty();
    RuleFor(x => x.EmailAddress).NotEmpty();
});

Or if using latest version c#

When(x => x.SendMail?.Equals("Y") ?? false, () =>
{
    RuleFor(x => x.To).NotEmpty();
    RuleFor(x => x.From).NotEmpty();
    RuleFor(x => x.EmailAddress).NotEmpty();
});

Upvotes: 2

Alexander V.
Alexander V.

Reputation: 1538

I would recommend to do something like this 

When(x => x.SendMail != null && x.SendMail.Equals("Y"), () =>
{
    RuleFor(x => x.To).NotEmpty();
    RuleFor(x => x.From).NotEmpty();
    RuleFor(x => x.EmailAddress).NotEmpty();
});

This way second condition of and statement (x.SendMail.Equals("Y")) evaluates only if first one (x.SendMail != null) is true. This rule it works for any boolean expression.

Upvotes: 3

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