FluentValidation rule for multiple properties

I have a FluentValidator that has multiple properties like zip and county etc. I want to create a rule that takes two properties just like a RuleFor construct

public class FooArgs
{
    public string Zip { get; set; }
    public System.Guid CountyId { get; set; }
}

public class FooValidator : AbstractValidator<FooArgs>
{
    RuleFor(m => m.CountyId).Must(ValidZipCounty).WithMessage("wrong Zip County");
}

This works but I want to pass both Zip and county to the rue in order to validate. What is the best method to achieve this?

Solution 1:

There is a Must overload that also provides you with the FooArgs object documented here. It allows you to easily pass both arguments into your method like this:

RuleFor(m => m.CountyId).Must((fooArgs, countyId) =>
    ValidZipCounty(fooArgs.Zip, countyId))
    .WithMessage("wrong Zip County");

Solution 2:

What about:

RuleFor(m => new {m.CountyId, m.Zip}).Must(x => ValidZipCounty(x.Zip, x.CountyId))
                                      .WithMessage("Wrong Zip County");

Solution 3:

Just came across this old question and I think I have a simpler answer. You can easily pass your whole object into your custom validation rule by simplifying the parameter to RuleFor e.g.

RuleFor(m => m).Must(fooArgs =>
    ValidZipCounty(fooArgs.Zip, fooArgs.countyId))
    .WithMessage("wrong Zip County");

If the ValidZipCountry method is local to your validator and you can change its signature to take a FooArgs then the code simplifies down to

RuleFor(m => m).Must(ValidZipCounty).WithMessage("wrong Zip County");

The only downside is that the PropertyName in the resultant validation error will be an empty string. This may cause a problem for you validation display code. However it is not really clear which property the error belongs too, ContryId or Zip, so this does make sense.