FluentValidation rule for multiple properties

Question

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

Answer 1

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.