我可以先使用Entity Framework代码为单个Collection属性创建单独的表吗？ [英] Can I create a separate table for a single Collection property using Entity Framework code first?

问题描述

我有一个 Foo 与 ICollection< string> 。为了能够通过实体框架存储这个，我创建了一个 Bar 与 Id 和 Value 属性。 Entity Framework创建一个 Bar 的表，其外键列为 Foo 。

问题是我有一大堆的类有这样 ICollection< string> 。我将它们全部转换为 ICollection< Bar> 。然而，结果是 Foo 表现在包含具有 ICollection< Bar> 的每个类的外键列， （10 +）。

虽然我知道有必要这样做以使这些关系在数据库中工作，但是数据库图表不会更直观。

我在想，就像在多对多的关系中，我想在每个关系之间有一张表。例如，

• 一个表 Foo_Bar ，有两列： Foo 和 Bar之间的关系的> Foo_Id 和 Bar_Id 和另一个表 Baz_Bar 与 Baz_Id 和 Bar_Id 。



为了实现这一点，我可以创建 Bar （例如 FooBar ）;更改集合以使用那些（例如 ICollection< FooBar> ）;并让EF使用每个类型的表创建数据库（例如通过 [Table（Foo_Bar）] FooBar >）方法。但我想防止必须创建所有这些空类。

我想知道是否可能以某种方式指定这个行为只是基于属性。类似的东西：

  public class Foo 
 {
 [Table（Foo_Bar）] 
 public ICollection< Bar>酒吧{get;组; } 
} 
  

注意：如果这种方法在第一个请

解决方案

总结评论：

你想要什么（即：5个表）是Entity Framework的一个多对多的关系。

按照惯例，你通过设置一个集合

  Foo {
 ICollection< Bar& bars 
} 
 
 Foo {
 ICollection< Foo> Foos 
} 
  

如果你不想反向集合通过流利的API设置关系。

  modelBuilder.Entity< Foo> .HasMany（x => x.Bars） .WithMany（）
  

AFAIK没有注释允许使用注释达到最后的结果。 / p>

然后你必须手工处理Foo的一个吧。解决方案可以是由EF创建的连接表的条形键的唯一约束。

I have a class Foo with an ICollection<string>. To be able to store this through Entity Framework, I have created a class Bar with an Id and Value property. Entity Framework creates a table for Bar with a foreign key column to Foo. This works well.

The problem is that I have a whole bunch of classes with such a ICollection<string>. I converted them all to ICollection<Bar>. The result however is that the Foo table now contains a foreign key column for every class that has an ICollection<Bar> (10+).

While I understand that it's necessary to do this to have those relationships work in the database, the database diagram doesn't get more intuitive this way.

I was thinking that, like in a many to many relationship, I would like to have a table in between each of those relationships. For example,

• a table Foo_Bar with two columns: Foo_Id and Bar_Id for the relationship between Foo and Bar and another table Baz_Bar with Baz_Id and Bar_Id.

To achieve this, I can create a sub class of Bar (e.g. FooBar) for every relationship; change the collection to use those (e.g. ICollection<FooBar>); and let EF create the database using the table per type (e.g. by decorating FooBar with [Table("Foo_Bar")]) approach for these types. But I would like to prevent having to create all these empty classes.

I wonder if it is possible to somehow specify this behaviour just based on the property. Something like this:

public class Foo
{
    [Table("Foo_Bar")]
    public ICollection<Bar> Bars { get; set; }
}

On a side note: If this approach is a bad idea in the first place, don't hesitate to let me know :).

解决方案

to summarize comments:

what you want (i.e.: 5 tables) is a many to many relation for Entity Framework.

By conventions you get it by setting a collection on both entities

Foo {
    ICollection<Bar> Bars
}

Foo {
    ICollection<Foo> Foos
}

if you don't want the reverse collections (Foos) then you have to setup the relation by the fluent API.

modelBuilder.Entity<Foo>.HasMany(x => x.Bars).WithMany()

AFAIK there is no annotation allowing to reach this last result by using the Annotations.

You then have to handle by hand the unicity of Foo for a Bar. A solution may be a unique constraint on the Bar Key of the join table created by EF.

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