如何使用FluentValidation有条件地验证属性？

Question

I'm trying to implement a rule using FluentValidation where two properties have a dependency on each other. They are Unit and UnitType . Unit is a string, and UnitType is an enum. I want rules where if the Unit is filled out then the UnitType cannot be None (0) , and if the UnitType is not None (0) then the Unit must be filled out. Here's the rules I've tried so far to no avail:

this.RuleFor(
    p =>
        p.Unit).NotEmpty().When(
    l =>
        (l.UnitType != UnitType.None)).WithMessage("Unit № must be filled out and must be less than 8 characters long when the Unit Type is selected");

this.RuleFor(
    p =>
        p.UnitType).NotEqual(UnitType.None).When(
    l =>
        !String.IsNullOrEmpty(l.Unit)).WithMessage("Unit Type must be selected when the Unit № is filled out");

No matter how I tweak the rules, I just keep getting an error that says: 'Unit Type' must not be empty. Since my custom error messages are not showing up, I'm thinking that the rules are being skipped somehow...

I'd appreciate any suggestions on how to get this fixed.

Answer 1

Well, after taking some time away from this and coming back to it, I believe I finally have it resolved. Originally in my post model I had the UnitType property as non-nullable, which is what was triggering the validation even though it's default value was UnitType.None . From what I can tell, MVC, not FluentValidation, sees that it's non-nullable property, ignores the default value and then attempts to bind the property anyway with a null value from the form post. I can kind of understand why it behaves this way, but can't help but think that it shouldn't ignore default values.

So, I changed the property to be nullable and now my two rules work as I expect them to. Still, I'm not overly happy about the way it actually works because I was hoping to use the default auto-generated value further down when mapping with AutoMapper, and now I'll have to make sure to set a default value in the constructor where it's relevant. Realistically a non-issue in the long run, so long as I don't miss setting a default somewhere.