流畅的 Nhibernate 表达式可在标记的枚举上进行选择

发布于 2024-08-27 23:51:31 字数 576 浏览 5 评论 0原文

我有一个域实体，它有一个标记的枚举作为属性。标记的枚举是这些实体的目标受众。然后，用户就有了他们应该看到的实体的标记枚举值。我试图找出正确的表达方式来选择满足用户目标受众的实体。

public class File
{
    public virtual TargetAudience TargetAudience { get; set; }
}

[Flags]
public enum TargetAudience
{
    Audience1 = 1,
    Audience2 = 2,
    Audience3 = 4,
    Audience4 = 8
}

表达式：（这在 IList 上执行时有效，但不适用于对数据库的查询。）

public Expression<Func<File, bool>> Expression
{
     get { return ((x.TargetAudience & UserTargetedAudience) > 0); }
}

任何建议都会有帮助。

原文

I have a domain entity that has a flagged enum as a property. The flagged enum is the target audience for the these entities. The user then has a flagged enum value of the entities they should see. I am trying to figure out the correct expression to select entities that meet the target audience for the user.

public class File
{
    public virtual TargetAudience TargetAudience { get; set; }
}

[Flags]
public enum TargetAudience
{
    Audience1 = 1,
    Audience2 = 2,
    Audience3 = 4,
    Audience4 = 8
}

Expression: (This works when performed on a IList<File>, but doesn't work on a query to the database.)

public Expression<Func<File, bool>> Expression
{
     get { return ((x.TargetAudience & UserTargetedAudience) > 0); }
}

Any suggestions would be helpful.

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落日海湾 2024-09-03 23:51:31

在对数据库的查询中它以什么方式不起作用？

您没有显示完整的实现或映射。您是否将 TargetAudience 保留为数字数据类型？

除非您跳过一些困难来执行此操作，否则您的枚举将作为文本存储在数据库中，因此您无法对其执行按位操作。（此行为与我在博客等中看到的一些内容相反，所以我不知道 (a) 自以前的版本以来它是否已更改，(b) 它是否对我正在使用的 SQLite 提供程序来说是唯一的，或 (c) 如果 Fluent NHibernate 以这种方式映射。）

您可以执行文本比较。组合标志存储为逗号分隔列表，因此 TargetAudience.Audience4 | TargetAudience.Audience1 将不会保留为 9，而是保留为 Audience1, Audience4。请注意，即使我以相反的顺序指定它们，它也会按升序保留。

var query = session.Linq<File>()
    .Where(f => f.TargetAudience.ToString() == "Audience1, Audience4");

您可以快速编写一些[扩展]方法来封装进行这些文本比较的麻烦。

编辑：

请参阅你怎么样使用流畅的 NHibernate 将枚举映射为 int 值？了解有关将枚举持久化为整数的信息

In what way does it not work in a query to the database?

You aren't showing your full implementation nor your mapping. Are you persisting TargetAudience as a numeric datatype?

Unless you are jumping through some hoops to do so, your enum will be stored as text in the database, so you can't perform bitwise operations on it. (This behaviour is contrary to some of what I've seen around blogs, etc., so I don't know (a) if it has changed since prior versions, (b) if it is somehow unique to the SQLite provider that I'm using, or (c) if it is mapped this way by Fluent NHibernate.)

You can perform a textual comparison. Combined flags get stored as a comma-separated list, so TargetAudience.Audience4 | TargetAudience.Audience1 would be persisted not as 9, but as Audience1, Audience4. Note that it gets persisted in ascending order, even though I specified them in reverse order.

var query = session.Linq<File>()
    .Where(f => f.TargetAudience.ToString() == "Audience1, Audience4");

You could write a few [extension] methods in short order that would encapsulate the nastiness of doing these textual comparisons.

edit:

See How do you map an enum as an int value with fluent NHibernate? for information about persisting enums as integers

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鲸落 2024-09-03 23:51:31

您可以使用 CustomType 方法将枚举属性映射为 int 列。

public class FileMap : ClassMap<File>
{
    Map( x => x.TargetAudience ).CustomType<int>();
}

// or the equivalent for automap
.Override<File>(map => {  
    map.Map( x => x.TargetAudience ).CustomType<int>();
});

You can map an enum property as an int column, with method CustomType.

public class FileMap : ClassMap<File>
{
    Map( x => x.TargetAudience ).CustomType<int>();
}

// or the equivalent for automap
.Override<File>(map => {  
    map.Map( x => x.TargetAudience ).CustomType<int>();
});

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