How to validation for complex property?

[GF-Huang]

For example:

public abstract class Animal : PropertyChangedBase { 
    public int Weight { get; set; }
}

public Cat : Animal { 
    public CatBreedsEnum CatBreeds { get; set; }
}

public Dog: Animal { 
    public DogBreedsEnum DogBreeds { get; set; }
}

public AnimalValidator : FluentValidation.AbstractValidator<Animal> {
    public AnimalValidator() => RuleFor(a => a.Weight).InclusiveBetween(1, 50);
}

public CatValidator : FluentValidation.AbstractValidator<Cat> {
    public CatValidator(AnimalValidator validator) { 
        Include(validator);
        RuleFor(c => c.CatBreeds).Equal(CatBreedsEnum.DragonLi); 
    }
}

public DogValidator : FluentValidation.AbstractValidator<Dog> {
    public DogValidator(AnimalValidator validator) { 
        Include(validator);
        RuleFor(d => d.DogBreeds).Equal(DogBreedsEnum.XXX); 
    }
}

public class ViewModel : ValidatingModelBase {
    public Animal MyPet { get; set; }

    public ViewModel(IModelValidator<ViewModel> validator) : base(validator) { }

    public void Save() {
        if (Validator()) // always true even if MyPet.Weight large than 50
            // ...
    }
}

public ViewModelValidator : FluentValidation.AbstractValidator<ViewModel> {
    public ViewModelValidator(CatValidator catValidator, DogValidator dogValidator) {
        RuleFor(vm => vm.MyPet).SetInheritanceValidator(v => {
             v.Add(catValidator);
             v.Add(dogValidator);
        });
    }
}

...
<TextBox Text="{Binding MyPet.Weight}" />
...

The other scaffold codes I make like https://github.com/canton7/Stylet/wiki/ValidatingModelBase. I'm not going to write it out.

The auto validation not work and Validate() always return True.

Do I need to modify Animal : PropertyChangedBase to Animal : ValidatingModelBase and set Validator by constructor?

[canton7]

What does GetErrors("MyPet") return?

[canton7]

It calls those methods on the IModelValidator

[GF-Huang]

ValidationDemo.zip

Here is demo project, could you help me to take a look why there is no red box around the TextBox even if validate failed?

[canton7]

Your validator returned a validation error for the property "MyPet.Weight". WPF doesn't understand that: it expects the property to be the name of a property on the object being validated. Since ShellViewModel is the object being validated, WPF expects the property names to be e.g. "MyPet".

[GF-Huang]

But is there any ways to solves this? In other words, make nested property validation works well and show red border around TextBox if there's error.

[canton7]

This is between you and WPF I'm afraid -- Stylet implements INotifyDataErrorInfo, and reports back the same property errors which your validator gives it. Maybe you can add some logic to FluentModelValidator so that all errors are truncated to the first ., so that MyPet.Weight gets turned into MyPet?