Interface as field in EntityFramework Core

Question

Is there a way to use interfaces as fields of a class in EF Core (CodeFirst, last version to day 5.0)?

say

public class Order
{
   public int Id { get; set;}
   public IUser CreatedBy { get; set; }
}

https://stackoverflow.com/questions/48250184/can-i-use-an-interface-as-a-property-with-entity-framework — Roman Ryzhiy, Jan 20 '21 at 14:13
@RomanRyzhiy, thanks. Should it be the same for EF Core as for the EF? — serge, Jan 20 '21 at 14:17
Not for navigation properties. With value conversions you could add an interface property to a model that is stored in a single field in the database. — Gert Arnold, Jan 21 '21 at 10:17
`Ivan Stoev` and `Palle Due` closing as duplicate a question asking about a different framework? Event the tags show it, never mind the first sentence saying `EF Core`. — Douglas Gaskell, Oct 26 '21 at 04:54

score 3 · Accepted Answer · answered Jan 20 '21 at 14:18

You can use interfaces for navigation properties, that are not exist in db. But for the Db columns you need the concrete classes.

In your case you have two way :

public class Order
{
[Key]
   public int Id { get; set;}
[ForeignKey]
   public int UserId CreatedBy { get; set; }
}

This way you can save UserId to Db and reuse it. This way is prefered.

Another way :

public class Order
{
   [Key]
   public int Id { get; set;}
   [NotMapped]
   public IUser CreatedBy { get; set; }
}

But this way IUser can be used as long as an Order instance exist im memory.

spasibo... any way, I see there are no perfect solutions for that case... — serge, Jan 20 '21 at 14:20

1 Answers1