The structure of my classes and repository:
public class Group{
//fields
}
public class User{
public UserRole Role {get;set;}
}
public abstract class UserRole{
//fields
}
public class PersonUserRole:UserRole{
public Group Group {get;set;}
}
public class ManagerUserRole:UserRole{
public IList<Group> Groups {get;set;}
}
An example where I encounter the issue:
public class UserRepository:IUserRepository{
private readonly ApplicationDbContext _dbContext;
private readonly DbSet<User> _users;
public UserRepository(ApplicationDbContext dbcontext)
{
_dbContext = dbcontext;
_users = _dbContext.DomainUsers;
}
public User GetBy(int id)
{
User type = _users.Include(u => u.Role)
.SingleOrDefault(c => c.UserId == id);
if (typeof(PersonUserRole) == type.Role.GetType())
{
return
_users.Include(u => u.Role)
.ThenInclude(r => (r as PersonUserRole).Groep)
.SingleOrDefault(c => c.UserId == id);
}
else
{
return _users.Include(u => u.Role)
.ThenInclude(r => (r as ManagerUserRole).Groups)
.SingleOrDefault(c => c.UserId == id);
}
}
}
I get the following error message:
Message "The property expression 'r => (r As PersonUserRole).Group' is not valid. The expression should represent a property access: 't => t.MyProperty'
It seems like I cannot cast my UserRole
Type to the actual PersonUserRole
Type to include the Group/Groups property. How can I include the properties of the subclasses?
Update: Starting with version 2.1, Include on derived types is now naturally supported by EF Core via either cast or as
operator inside lambda Include
/ ThenInclude
overloads or string
Include
overload.
Original answer (pre EF Core 2.1):
Currently eager loading of derived entity navigation properties is not supported.
As a workaround you can use a combination of Eager loading, Explicit loading and Querying related entities explained in the Loading Related Data section of the EF Core documentation:
var user = _users.Include(u => u.Role).SingleOrDefault(u => u.UserId == id);
var userRoleQuery = db.Entry(user).Reference(u => u.Role).Query();
if (user.Role is ManagerUserRole)
userRoleQuery.OfType<ManagerUserRole>().Include(r => r.Groups).Load();
else if (user.Role is PersonUserRole)
userRoleQuery.OfType<PersonUserRole>().Include(r => r.Group).Load();
return user;
EntityFramework has an open issue which is exacly the same as your problem: https://github.com/aspnet/EntityFramework/issues/3910
Maybe you can try what they suggest, but I can't try if it works:
var o = context.Set<Order>() .Where(o => o.Id == 1234) .Single(); context.Set<GroupPosition>() .Where(x => x.Order == o) .Include(x => x.GroupType) .Load(); context.Set<SalesPosition>() .Where(x => x.Order == o) .Include(x => x.Group) .Load();