Multiple Inheritance Levels in EF Code Firs

Question

I am trying to figure out how to handle inheritance for multiple types. I have an existing Code First / EF / MVC project which has live data in a production environment. The sys

Answer 1

Inheritance could be tricky in many ways - so my advice is to go 'easy' with it.

But just doing a typical OO design here will produce usable tables, structure. Maybe something like this could work for you...

public class Document
{
    public long ID { get; set; }
    public string Name { get; set; }
}

public class OrderLinesDocument : Document
{
    public ICollection<OrderLine> OrderLines { get; set; }
}

public interface IVendorDocument
{
    ICollection<Vendor> Vendors { get; set; }
}
public class VendorDocument : Document, IVendorDocument
{
    public ICollection<Vendor> Vendors { get; set; }
}

public interface ICustomerDocument
{
    ICollection<Customer> Customers { get; set; }
}
public class CustomerDocument : Document
{
    public ICollection<Customer> Customers { get; set; }
}

public class PurchaseOrder : OrderLinesDocument, IVendorDocument
{
    public ICollection<Vendor> Vendors { get; set; }
}

public class Invoice : Document, ICustomerDocument
{
    public ICollection<Customer> Customers { get; set; }
}

The simplest solution IMO is using TPH (just 'as is' pretty much).

But as I said, careful with it - and it might not work for what you have in mind - i.e. you'd need to experiment, make sure Db records look optimal.

btw. you can use it like this if you didn't know, forgot to post that...

var query1 = db.Documents.OfType<PurchaseOrder>().ToList();
var query2 = db.Documents.OfType<Invoice>().ToList();

var query3 = db.Documents.OfType<CustomerDocument>().ToList();
var query4 = db.Documents.OfType<VendorDocument>().ToList();
var query5 = db.Documents.OfType<OrderLinesDocument>().ToList();

var query6 = db.Documents.OfType<Document>().ToList();

(try that to see how it actually works)