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Adding a new child when changing an existing child structure

I look at some answers to similar questions, and they really do not suit me.

I am trying to include a template from Entity Framework: DbContext (p. 90) and it does not seem to work. The code I'm using is below:

[HttpPost]
public ActionResult Edit(Order order)
{
     if (ModelState.IsValid)
     {
         db.Orders.Add(order);
         db.Entry(order).State = EntityState.Modified;

         foreach (var orderDetail in order.OrderDetails)
         {
              if (orderDetail.OrderId == 0)
              {
                  db.Entry(orderDetail).State = EntityState.Added;
              }
              else
              {
                  db.Entry(orderDetail).State = EntityState.Modified;
              }
              // The example order that I'm updating has two child entities
              // so this orderId will be for the third, added one.
              int addedOrderDetailId = order.OrderDetails[2].OrderId;
          }
          db.SaveChanges();
          return RedirectToAction("Index");
     }

     ViewBag.CustomerId = new SelectList(db.Customers, "CustomerId", "CompanyName", order.CustomerId);

     return View(order);

}

I used an example in which an Order object has two existing OrderDetail objects, and I'm trying to add a third one. I turned on the addedOrderDetailId variable to add it to Watch and see when it changed.

, OrderId OrderDetail ( 0, foreach) OrderId Order. foreach ( . , . SaveChanges(), , .

- , , . , , , , - , .

Edit:

Slauma db.Orders.Add(). db.Entry(order).State foreach. OrderDetail . OrderId OrderId , . , . , , . :

    [HttpPost]
    public ActionResult Edit(Order order)
    {
        if (ModelState.IsValid)
        {
            List<int> previousProductIds = db.OrderDetails
                .Where(ep => ep.OrderId == order.OrderId)
                .Select(ep => ep.ProductId)
                .ToList();

            List<int> currentProductIds = order.OrderDetails
                .Select(o => o.ProductId)
                .ToList();

            List<int> deletedProductIds = previousProductIds
                .Except(currentProductIds).ToList();


            foreach (var deletedProductId in deletedProductIds)
            {
                OrderDetail deletedOrderDetail = db.OrderDetails
                    .Where(od => od.OrderId == order.OrderId && od.ProductId == deletedProductId)
                    .Single();

                db.Entry(deletedOrderDetail).State = EntityState.Deleted;
            }

            foreach (var orderDetail in order.OrderDetails)
            {
                if (orderDetail.OrderId == 0)
                {
                    db.Entry(orderDetail).State = EntityState.Added;
                    orderDetail.OrderId = order.OrderId;
                }
                else
                {
                    db.Entry(orderDetail).State = EntityState.Modified;
                }
            }
            db.Entry(order).State = EntityState.Modified;
            db.SaveChanges();
            return RedirectToAction("Index");
        }
        ViewBag.CustomerId = new SelectList(db.Customers, "CustomerId", "CompanyName", order.CustomerId);
        return View(order);
    }
+5
1

:

db.Orders.Add(order);

, orderDetails, Added. ( Add) OrderId OrderDetails . orderDetail.OrderId, != 0 , , Modified. orderDetail Added, .

+1

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