EF v4 Mapping relationship without primary key - DB First

Question

I am currently working with a database that pulls information from another system into it for manipulation. I decided to use Entity Framework and the DB first approach to comprise my data access. One of the unique things about the project is that I am using the buisness key from the external system as the key that will show up in associated tables but it isn't the primary key in my system. I use this key for the relationships in the associated tables EG MyTable.ExternalId --> Review.ExternalId (ExternalId IS NOT the pk in parent table). Because of this, EF doesn't recongize the relationship even though I have a foreign key constraint on the child table making this relationship known in the database.

Is there a way to override EF to tell it to use the ExternalId instead of the PK to build the relationship? Or would it be suggested that I just change the relationship to use the PK of the parent table?

You can add a new navigation property by right-clicking your entities and selecting "Add new navigation-property." Then, in the properties window, you select the foreign key you need to navigate to in the select box. Does this approach work with foreign keys that do not point to primary keys? i do consider it bad practice to create entities based on foreign keys that arent primaries. You should just use queries to get those instead of navigational properties in my opinion. — Jente Rosseel
– Jente Rosseel, Commented Apr 2, 2013 at 13:39
@jrosseel The designer shows the foreign keys, but it doesn't show keys that aren't a pk in another table. The ExternalId does have a unique index on it. I do see what you are saying about the query though. — Justin
– Justin, Commented Apr 2, 2013 at 13:46

Ladislav Mrnka · Accepted Answer · 2013-04-02 18:07:50Z

1

EF doesn't support unique keys yet so you cannot use your ExternalId as identification of principal record in the database. You either have to use ExternalId as PK in your table or build relation with the real PK of the principal table.

answered Apr 2, 2013 at 18:07

Ladislav Mrnka

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