I'm using EF Core 3.0 with .NET Core 3.0. I have an abstract database model that is inherited by 2 classes. Each one has its own table
So we have Class A as the abstract, and class B and C are inheriting A. B and C have separate tables in the database. they are identical and add no extra fields.
Now here is the problem.
if I try to get a list of Bs from the database as following:
List<A> list = await context.Bs.ToListAsync();
this works perfectly fine, the following also works:
A a = context.Bs.FirstOrDefault();
However, the following cause an exception:
A a = await context.Bs.FirstOrDefaultAsync();
This is the exception:
System.ArgumentException: Expression of type 'System.Threading.Tasks.Task`1[B]' cannot be used for return type 'System.Threading.Tasks.Task`1[A]'
I think this is due to the fact that IList is defined to be covariant while System.Task isn't
so, is there a way to workaround this? as far as I know EF core supports inheritance just fine, so how is it supposed to be used if this was wrong?
EDIT:
I didn't mention an important aspect to complicated the problem even more.
in the provided examples above I used context.Bs directly, this simplifies the problem since I know I'm using B.
However in my case I have something called IUserManager, the user manager will resolve the DbSet dynamically, so it will be something like this:
IUserManager manager = GetDynamicVersion();
A a = await manager.UsersTable.FirstOrDefaultAsync();
In this scenario, manager.UsersTable will return IQueryable<A>
