EF CTP4 Tips & Tricks: Code First Inheritance Mapping

Thanks for the excellent post! Just one question: In TPC, do you create a table in DB for the abstract type (e.g. Product) as well? My understanding is that when it comes to TPC, we only use FluentAPI to map concrete types and the abstract base class would only exist in our object model and that’s why there is no FK between tables in DB. Having said that, I assume that in your example Product is not an abstract type and the screen shot from DB confirms that, however have a DbSet of Product in the Context contradict it. Can you please advise?

I am a newbie in EF4 code first and MVC.

I read this article with interest and decided to try out the example in Table per Type.

I add in some interface and save the code as Tpt Model.cs and then add ProductController, DiscontinuedProductController and produce the Index, Create and Edit views on the ProductController and Index and Create Views on the other controller.

When I ran the project by calling for Product an empty database was created with 3 tables: Products, DiscontinuedProducts, and MetadataModel.

I was able to add in rows to the 2 tables Products and DiscontinuedProducts.

Well, the entries to the Products table are OK. But the Discontinuedproduct table has a life of its own and doesn’t behave correctly, or at least not as I expect it to be.

I entered 3 products into the Products table. Since the column [Datediscontinued] is not in the Products table I thought I could enter the info in the other table. Since the products are not discontinued there is nothing to show in the Index view. So I tried to [create] a discontinued product by clicking the [Create] button that brought me to the [Create] view.

The result is that the ProductId took a new value, in this case [4] after the last value, which was [3] in the Products table and not the ProductId, [1], which I entered for the product I want it to discontinue.

What have I done wrong?

How to modify the codes to make this work?

Any suggestion is most welcome.

The codes I used are attached below for your reference:

1. TptModel.cs \:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Globalization;
using System.Linq;
using System.Web;
using System.Web.Mvc;
using System.Web.Security;

using System.Data.Entity;
using System.Data.Entity.ModelConfiguration;

namespace MvcTpt.Models
{

public interface IProductContext
{
IDbSet Products { get; }
IDbSet DiscontinuedProducts { get; }
int SaveChanges();
}

public class ProductContext : DbContext, IProductContext
{

public IDbSet Products { get; set; }
public IDbSet DiscontinuedProducts { get; set; }

protected override void OnModelCreating(ModelBuilder modelBuilder)
{

modelBuilder.Entity()

.MapHierarchy(p => new

{

p.ProductId,

p.Name,

p.UnitPrice,

})

.ToTable(“dbo.Products”);

modelBuilder.Entity()

.MapHierarchy(d => new

{

d.ProductId,

d.DiscontinuedDate,

})

.ToTable(“dbo.DiscontinuedProducts”);

}
}

public class Product
{

public int ProductId { get; set; }

public string Name { get; set; }

public decimal UnitPrice { get; set; }

}

public class DiscontinuedProduct : Product
{

public DateTime ? DiscontinuedDate { get; set; }

}

}

2. ProductController:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

using MvcTpt.Models;

namespace MvcTpt.Controllers
{
public class ProductController : Controller
{
//
// GET: /Product/

private IProductContext context;

public ProductController()
{
this.context = new ProductContext();
}
public ProductController(IProductContext context)
{
this.context = context;
}

public ActionResult Index()
{
return View(this.context.Products.OrderBy(d => d.ProductId).ToList());
}

public ViewResult Create()
{
return View();
}

[HttpPost]
public ActionResult Create(Product dep)
{
context.Products.Add(dep);
context.SaveChanges();
return RedirectToAction(“Index”);
}

// GET: /Products/Edit/5
public ActionResult Edit(int ProductId)
{
return View(context.Products.Find(ProductId));
}

// POST: /Products/Edit/5
[HttpPost]
public ActionResult Edit(int ProductId, FormCollection collection)
{
var prd = context.Products.Find(ProductId);
UpdateModel(prd);
context.SaveChanges();
return RedirectToAction(“Index”);
}

}
}

3. DiscontinuedProductController:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.Mvc;

using MvcTpt.Models;

namespace MvcTpt.Controllers
{
public class DiscontinuedProductController : Controller
{
//
// GET: /DiscontinuedProduct/

private IProductContext context;

public DiscontinuedProductController()
{
this.context = new ProductContext();
}
public DiscontinuedProductController(IProductContext context)
{
this.context = context;
}

public ActionResult Index()
{
return View(this.context.DiscontinuedProducts.OrderBy(d => d.ProductId).ToList());

}

public ViewResult Create()
{
return View();
}

[HttpPost]
public ActionResult Create(DiscontinuedProduct dep)
{
context.DiscontinuedProducts.Add(dep);
context.SaveChanges();
return RedirectToAction(“Index”);
}
}
}