如何直接对List<T>进行验证？

Question

我有一个模型类：

public class MyModel() { //properties here... }

我想要验证一个MyModel对象的列表。因此我创建了这个验证器：

class MyModelListValidator : AbstractValidator<List<MyModel>>
{
    public MyModelListValidator ()
    {
        RuleFor(x => x)
            .SetCollectionValidator(new MyModelValidator())
            .When(x => x != null);
    }

    private class MyModelValidator : AbstractValidator<MyModel>
    {
        public MyModelValidator()
        {
            //MyModel property validation here...
        }
    }
}

但是上面的方法不起作用。一个替代方案是创建一个类，例如：

public class MyModelList()
{
    public List<MyModel> Items { get; set; }
}

这样也可以实现。但是有没有一种不使用额外类的方法呢？

- Ivan-Mark Debono

---

如果您的操作以 List<MyModel> 作为参数，您可以定义 AbstractValidator<MyModel>，fluentvalidation 将自动将其应用于列表中的每个项目。 - Aleksey L.

Answer 1

如果您正在使用数据注释来执行验证，则可能需要自定义属性：

public class EnsureOneElementAttribute : ValidationAttribute
{
    public override bool IsValid(object value)
    {
        var list = value as IList;
        if (list != null)
        {
            return list.Count > 0;
        }
        return false;
    }
}

然后：

[EnsureOneElement(ErrorMessage = "At least a person is required")]
public List<Person> Persons { get; private set; }
or to make it more generic:

public class EnsureMinimumElementsAttribute : ValidationAttribute
{
    private readonly int _minElements;
    public EnsureMinimumElementsAttribute(int minElements)
    {
        _minElements = minElements;
    }

    public override bool IsValid(object value)
    {
        var list = value as IList;
        if (list != null)
        {
            return list.Count >= _minElements;
        }
        return false;
    }
}

然后：

[EnsureMinimumElements(1, ErrorMessage = "At least a person is required")]
public List<Person> Persons { get; private set; }
Personally I use FluentValidation.NET instead of Data Annotations to perform validation because I prefer the imperative validation logic instead of the declarative. I think it is more powerful. So my validation rule would simply look like this:

RuleFor(x => x.Persons)
    .Must(x => x.Count > 0)
    .WithMessage("At least a person is required");

- Melih Yilman