实体框架代码具有指向单个表的多个一对多关系的第一个配置

Question

I am building an application with many different objects (tables), many of which have a need to have a one-to-many relationship to an "Attribute" object. For example, I could have five different objects - A, B, C, D, E - and each of these needs to have an Attributes property - A.Attributes, B.Attributes, etc.

My question is, how would be the best way to structure this in EF Code First? This Attribute class may end up having 15-20 different classes that have a relationship with it.

Currently, a configuration for one of the "parent" classes looks like this:

        HasMany(rdp => rdp.Attributes)
            .WithOptional()
            .WillCascadeOnDelete();

However, this will create a foreign key column on the Attribute table (eg, "A_Id", "B_Id", etc). So if I have 20 different classes with attributes, the Attribute table will have 20 different foreign keys.

Is there any better way to structure this?

Answer 1

You could introduce an AttributeList type that maps to its own table. Ie you could model the list as an entity.

A, B, C, D, E would have a one-to-one association to the AttributeList, with the foreign key to the AttributeList on the A, B, C, D and E classes.

Each AttributeList object contains many attributes, or in other words there is a one-to-many relationship from AttributeList to Attribute.

Now you have a single type with one-to-many to the Attributes and you only need a single foreign key to the AttributeList on the attributes.