FluentNHibernate：当许多是简单枚举时如何处理一对多值

发布于 2024-09-16 23:29:40 字数 545 浏览 4 评论 0原文

看起来以下情况应该并不罕见，但我不知道如何在 FluenNHibernate 中处理它：

public class Product: BaseEntity
{
    public Product()
    {
        Categories = new List<Category>();
    }

    public virtual IList<Category> Categories { get; set; }
    ...
}

public enum Categories
{
    Classic = 1,
    Modern = 2,
    Trendy = 3,
    ...
}

所以，我需要一个 ProductCategories 表，它允许我将一个产品映射到多个类别，但我不认为NHibernate 将处理这个问题，除非我有一个实际的类别类和一个指定了多对多关系的类别表。这样做不可取的原因有很多，其中最重要的是它太过分了。

我正在使用 AutoMapper - 有什么方法可以覆盖以使其工作吗？

谢谢！

原文

It seems like the following scenario shouldn't be uncommon, but I can't figure out how to handle it in FluenNHibernate:

public class Product: BaseEntity
{
    public Product()
    {
        Categories = new List<Category>();
    }

    public virtual IList<Category> Categories { get; set; }
    ...
}

public enum Categories
{
    Classic = 1,
    Modern = 2,
    Trendy = 3,
    ...
}

So, I need a ProductCategories table that allows me to map one product to many categories, but I don't think NHibernate will handle this unless I have an actual Categories class and a Categories table with a many-to-many relationship specified. There are a number of reasons this is not desirable, not the least of which is that it's overkill.

I'm using AutoMapper - any way I can override to make this work?

Thanks!

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新雨望断虹 2024-09-23 23:29:40

这个接受的答案对我有用，但是枚举被映射为 int 。

为了将其映射为字符串（我的偏好），我调整了映射，如下所示：

public void Override(AutoMapping<Account> mapping)
{
    mapping
        .HasMany(x => x.Categories)
        .Table("CategoriesProductsMap")
        .Element("Category", e => e.Type<NHibernate.Type.EnumStringType<Category>>())
        .AsSet();
}

This accepted answer worked for me, however the enum was mapped as in int.

To get it to map as a string (my preference) I adapted the mapping as follows:

public void Override(AutoMapping<Account> mapping)
{
    mapping
        .HasMany(x => x.Categories)
        .Table("CategoriesProductsMap")
        .Element("Category", e => e.Type<NHibernate.Type.EnumStringType<Category>>())
        .AsSet();
}

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心凉 2024-09-23 23:29:40

我曾在像这样的另一个实例中尝试过连接字符串，但我真的想要一些不需要每次都进行转换的东西。事实证明，我在这里发现了一个非常相似的问题： Map to a list of Enums? 。如那里所述，此覆盖有效：

public void Override(AutoMapping<Product> mapping)
{
     mapping.HasMany(x => x.Categories).KeyColumn("ProductFk").Table("CategoriesProductsMap").Element("Category").AsBag();
}

I had tried the concatenated string in another instance like this, but I really wanted something that didn't need to be transformed every time. As it turns out, I found a very similar question here: Map to a list of Enums?. As described there, this override works:

public void Override(AutoMapping<Product> mapping)
{
     mapping.HasMany(x => x.Categories).KeyColumn("ProductFk").Table("CategoriesProductsMap").Element("Category").AsBag();
}

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静水深流 2024-09-23 23:29:40

有几种方法可以做到这一点，但没有一种方法像您想象的那么简单。虽然 NHibernate 和 Fluent NHibernate 在使用单个 enum 时表现得很好，但集合则明显更麻烦。

以下是几种方法：

通过连接成员将集合保留到单个 nvarchar(?) 列。
使用 Flags 属性标记 enum 并将列表折叠为位掩码（这将只需要一个整数列）

在任何一种情况下，您都可以让 NHibernate 访问包含以下内容的字段： “折叠”值；公共属性的 getter 会将折叠的值转换为集合。折叠值的 getter 会将集合转换为单个字符串 (1) 或整数 (2)。

您必须显式映射 Product：

public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Id(x => x.Id);

        Map(Reveal.Member<Product>("_categories"))
            .Access.Field();
    }
}

因此，尽管 Product 公开了 IList，NHibernate 只会获取和设置_categories 字段；

There are a few ways to do this, none of them as straightforward as you might expect. While NHibernate and Fluent NHibernate do quite well with a single enum, a collection is significantly more troublesom.

Here are a couple of approaches:

Persist the collection to a single nvarchar(?) column by concatenating the members.
Mark the enum with the Flags attribute and collapse the list as a bitmask (this will require just one integer column)

In either case, you can have NHibernate access a field that contains the "collapsed" values; the getters of the public properties will transform the collapsed values to collections. The getter of the collapsed value will transform the collection into a single string (1) or integer (2).

You'd have to map Product explicitly:

public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Id(x => x.Id);

        Map(Reveal.Member<Product>("_categories"))
            .Access.Field();
    }
}

So although Product exposes an IList<Category>, NHibernate will only get and set the value of the _categories field;

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