FluentValidation 检查子集合中的重复实体

我有一个MainEntity类，它有一个集合SubEntity。目前的验证情况如下：

public class MainEntityValidator : AbstractValidator<MainEntity>
{
    public MainEntityValidator()
    {
        RuleFor(x => x.SubEntities).SetCollectionValidator(new SubEntityValidator());
    }

    public class SubEntityValidator : AbstractValidator<SubEntity>
    {
        public SubEntityValidator()
        {
            RuleFor(x => x.Field1).NotNull();
            RuleFor(x => x.Field2).NotNull();
        }
    }
}

如何添加验证规则以便只有唯一的SubEntity对象（基于Field1 and Field2) 必须在集合中吗？

如果您需要将验证规则应用于集合属性，但仍然需要访问主模型和（或）整个集合，而不仅仅是正在验证的项目，那么RuleForEach方法是你的选择：

var comparer = new SubEntityComparer();

RuleForEach(x => x.SubEntities)
    .Must((model, submodel) => model.SubEntities.Count(xsub => comparer.Equals(xsub, submodel)) == 1) // one match that ReferenceEquals hit
    .WithMessage("The item with values {0}, {1} has duplicates in collection of {2} items",
        (model, submodel) => submodel.Field1,
        (model, submodel) => submodel.Field2,
        (model, submodel) => model.SubEntities.Count); // in validation message generation you can access to current item as well as to main model

如果您描述的验证规则只需要一条错误消息 - 您可以将简单的谓词规则应用于集合属性SubEntites:

RuleFor(x => x.SubEntities)
    .Must(coll => coll.Distinct(new SubEntityComparer()).Count() == coll.Count)
    .WithMessage("One or more items in collection of {0} items are duplicates",
        (model, coll) => coll.Count); // has access to collection and to main model

在这两种情况下，我都使用相同的相等比较器，但您可以覆盖Equals方法也是如此，并使用重载IEnumerable具有重载的扩展方法，排除EqualityComparer范围。

EqualityComparer的代码如下：

public class SubEntityComparer : IEqualityComparer<SubEntity>
{
    public bool Equals(SubEntity x, SubEntity y)
    {
        if (x == null ^ y == null)
            return false;

        if (ReferenceEquals(x, y))
            return true;

        // your equality comparison logic goes here:
        return x.Field1 == y.Field1 &&
               x.Field2 == y.Field2;
    }

    public int GetHashCode(SubEntity obj)
    {
        return obj.Field1.GetHashCode() + 37 * obj.Field2.GetHashCode();
    }
}

Update:

在这两种实现集合验证的方法中，您仍然可以使用SetCollectionValidator(new SubEntityValidator())使用简单的规则独立验证每个项目。