MVC 5 Scaffolding Code generation with an Inherited Entity causes System.Core already imported

Question

I have used Entity Framework DB First approach to create my model. I spent many hours fighting with the EDMX to set up the inheritance correctly (0 errors). Then now when trying to create either an MVC 5 Controller w/ Views using EF, or add a View for the inheriting class I revieve this error:

There was an error running the selected code generator:

'There was an error in compilation of the type 'CostaPropertyServices.Models.PropertyInfoEntities'.

CS1703: An assembly with the same identity 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' has already been imported. Try removing one of the duplicate references.'

I have two classes: Person and Vendor. Vendors inherit from Persons, and add only an int ID field named PackageID.

If anyone has any idea why I would really appreciate it. EF Inheritance seems to have been much more trouble than it's worth so far. Many Thanks.

Edit: Maybe I'm not supposed to be generating the views for inheriting entities? Or maybe I've not configured the inheritance correctly (Not set base to abstract?)

---

Person.cs

namespace CostaPropertyServices.Models
{
    using System;
    using System.Collections.Generic;

    public partial class Person
    {
        public int PersonID { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public string Email { get; set; }
        public string Phone { get; set; }
        public string Mobile { get; set; }
        public Nullable<System.DateTime> Created { get; set; }
        public Nullable<System.DateTime> Modified { get; set; }
        public Nullable<System.DateTime> Deleted { get; set; }
    }
}

Vendor.cs

namespace CostaPropertyServices.Models
{
    using System;
    using System.Collections.Generic;

    public partial class Vendor : Person
    {
        public int PackageID { get; set; }
    }
}

Answer 1

I've found a solution! Well, to let me add controllers and views for the entity at least. I'll describe it briefly for anyone who is stuck on this too, however I plan to come back and expand this answer as soon as time allows.

It so happens that scaffolding worked completely fine with non-inheriting entities, and my project didn't seem to contain any references to System.Core, let alone a duplicate one. This made me think it was a compatibility issue with inheritance and the default scaffold-er.

Steps to Fix:

1. Install MVCScaffolding using NuGet.

   PM> Install-Package MvcScaffolding
   

2. Run the following command via Package Manager Console

   PM> Scaffold Controller Vendor -Repository
   

   Edit: Pass -DbContextType [YourProjectEntities] to specify a DbContext to update rather than it creating a new one you probably don't want.

3. Update methods in generated VendorRepository.cs to use Persons table and not (non-existant) Vendors table. Below was my result:

   public class VendorRepository : IVendorRepository
   {
       PropertyInfoEntities context = new PropertyInfoEntities();
   
       public IQueryable<Vendor> All
       {
           get { return context.Persons.OfType<Vendor>(); }
       }
   
       public IQueryable<Vendor> AllIncluding(params Expression<Func<Vendor, object>>[] includeProperties)
       {
           IQueryable<Vendor> query = context.Persons.OfType<Vendor>();
           foreach (var includeProperty in includeProperties) {
               query = query.Include(includeProperty);
           }
           return query;
       }
   
       public Vendor Find(int id)
       {
           return context.Persons.OfType<Vendor>().SingleOrDefault(v => v.PersonID == id);
       }
   
       public void InsertOrUpdate(Vendor vendor)
       {
           if (vendor.PersonID == default(int)) {
               // New entity
               context.Persons.Add(vendor);
           } else {
               // Existing entity
               context.Entry(vendor).State = System.Data.Entity.EntityState.Modified;
           }
       }
   
       public void Delete(int id)
       {
           var vendor = context.Persons.OfType<Vendor>().SingleOrDefault(v => v.PersonID == id);
           context.Persons.Remove(vendor);
       }
   
       public void Save()
       {
           context.SaveChanges();
       }
   
       public void Dispose() 
       {
           context.Dispose();
       }
   }
   

4. Eureka!

NOTE: See this blog for standard usage, tips and customisation.