获取 EF TPT 继承中的实体类型

Question

My domain entities are using EF Table Per Type Inheritance, and here is the relationship.

As you can see Invoices sits on the parent entity Order.cs . This is now creating me issues when I deal with invoices.

For instance, to create an invoice , I need to pass the order Id to the Invoice controller:

public ActionResult Create(int orderId)
{
  if (orderId == 0) return new HttpStatusCodeResult(HttpStatusCode.BadRequest);

  // determine whether the order is a SaleOrder or a PurchaseOrder
  // then create the viewModel passing in the SaleOrder / PurchaseOrder details
  return View(viewModel);
}

How do I figure out what child type an order is by simply its Id?

UPDATE

Theo asked how I was currently retrieving SaleOrders and PurchaseOrders. I have this in my context:

public DbSet<PurchaseOrder> PurchaseOrders { get; set; }
public DbSet<SaleOrder> SaleOrders { get; set; }

I have built a repository around each, so I have a PurchaseOrderRepository and a SaleOrderRepository and I do my CRUD that way.

Answer 1

If the two classes inherit from the same class you can create another DbSet

public DbSet<Order> Orders { get; set; }

and in your Action ask for the order like this

    public ActionResult Create(int orderId)
    {
      if (orderId == 0) return new HttpStatusCodeResult(HttpStatusCode.BadRequest);
      var order = db.Orders.Find(orderId);
      if(order is SaleOrder){
        //do your stuff for SaleOrder
      }
      if(order is PurchaseOrder){
        //do your stuff for PurchaseOrder
      }          
      return View(viewModel);
    }