How to not declare key in root model in EntityFramework core

Question

I would like to create a base model with some common fields for all tables, like CreatedBy and ModifiedBy, but I don't want to add the key to that base model.

public abstract class BaseModel
{
    public string CreatedBy { get; set; }

    public string ModifiedBy { get; set; }
}

public class Student : BaseModel
{
    [Key, Column(Order = 0)]
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int Id { get; set; }

    public string FirstName { get; set; }
}

I am getting this error message

The derived type cannot have KeyAttribute on property 'Id' since the primary key can only be declared on the root type

.

I am using Entity Framework Core 2.

Just don't map the `BaseModel` class, only map the sub classes. Or don't use a base class and visible properties at all. These properties are perfect candidates for [shadow properties](https://stackoverflow.com/a/52021425/861716) — Gert Arnold, Sep 07 '18 at 10:36
The main motivation for all of this is to add IsDeleted property in the BaseModel and to have Query filter like this `modelBuilder.Entity().HasQueryFilter(p => !p.IsDeleted)` is there any way to implement this — Mirhat, Sep 07 '18 at 12:34
Yes. This answer on Soft Delete with Shadow Properties and Query Filters: https://stackoverflow.com/questions/47673524/ef-core-soft-delete-with-shadow-properties-and-query-filters — David Browne - Microsoft, Sep 07 '18 at 13:55
@Mirhat problem is in your `DbContext` class. Please share your `DbContext` class code. — TanvirArjel, Sep 07 '18 at 17:53

score 2 · Answer 1 · answered Apr 29 '19 at 12:43

I have received the same error and came here. Your code is not complete, but I can provide some insight based on what I have experienced. Possible causes:

DbSet<BaseModel> in your context
Foreign key involving base model:

[ForeignKey(nameof(BaseModel)] public int SomeId { get; set; }

public BaseModel SomeNavigationProperty { get; set; }
Some (navigation) property using BaseModel in any of your models (used in the db context)

public BaseModel SomeModel { get; set; }

All these will make add-migration think that BaseModel is a model to be added and dealt with in the database context and will generate this error.

How to not declare key in root model in EntityFramework core

1 Answers1