Entity Framework Inheritance with EntityFramework (Code First) Table per type
Example
This approach will generate (n+1) tables on the database to represent all the inheritance structure where n is the number of subclasses.
How to:
public abstract class Person
{
public int Id { get; set; }
public string Name { get; set; }
public DateTime BirthDate { get; set; }
}
[Table("Employees")]
public class Employee : Person
{
public DateTime AdmissionDate { get; set; }
public string JobDescription { get; set; }
}
[Table("Customers")]
public class Customer : Person
{
public DateTime LastPurchaseDate { get; set; }
public int TotalVisits { get; set; }
}
// On DbContext
public DbSet<Person> People { get; set; }
public DbSet<Employee> Employees { get; set; }
public DbSet<Customer> Customers { get; set; }
The table generated will be:
Table: People Fields: Id Name BirthDate
Table: Employees Fields: PersonId AdmissionDate JobDescription
Table: Customers: Fields: PersonId LastPurchaseDate TotalVisits
Where 'PersonId' on all tables will be a primary key and a constraint to People.Id
Advantages
- Normalized tables
- Easy to add columns and subclasses
- No nullable columns
Disadvantages
- Join is required to retrieve the data
- Subclass inference is more expensive
