Question

I have a model created using Model First approach. When I try to access the Book entity using the context it is not listed there; but the selling item is listed. What change need to be done inorder to add the Book entity to the context?

Note: Please read Adding reference to entity causing Exception and Entity Framework: Get Subclass objects in Repository for further details.

Model

Code

    static void Main(string[] args)
    {
        string connectionstring = "Data Source=.;Initial Catalog=NerdDinners;Integrated Security=True;Connect Timeout=30";
        using (var db = new MyModelFirstTestContainer(connectionstring))
        {
            Book book = new Book();
            book.AvailabilityStatus = "Available";
            book.Price = 100;
            book.Title = "World visit";

           //db.


        }

Answer 1

The Entity Framework does not create separate ObjectSets for inherited items on your Context.

Instead you can use the OfType<T>() method like this:

from b in db.SellingItems.OfType<Book>()
where b.Title = "my title"
select b;

Here is the MSDN Documentation for OfType

If you want to add an inherited entity you will use the parent ObjectSet.

Book b = ...;
db.SellingItems.Add(b);
db.SaveChanges();