c# - 列表的 ViewModel 验证

Question

我有以下 View 模型定义

public class AccessRequestViewModel
{
    public Request Request { get; private set; }
    public SelectList Buildings { get; private set; }
    public List<Person> Persons { get; private set; }
}

因此在我的应用程序中必须至少有 1 个人进行访问请求。您可以使用什么方法来验证？我不希望这种验证发生在我的 Controller 中，这很容易做到。唯一的选择是自定义验证属性吗？

编辑:目前正在使用 FluentValidation(不错的库!)执行此验证

RuleFor(vm => vm.Persons)
                .Must((vm, person) => person.Count > 0)
                .WithMessage("At least one person is required");

Answer 1

如果您使用数据注释来执行验证，您可能需要一个自定义属性:

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; }

或者让它更通用:

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; }

我个人使用 FluentValidation.NET而不是数据注释来执行验证，因为我更喜欢命令式验证逻辑而不是声明式。我认为它更强大。所以我的验证规则看起来像这样:

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