create new record via entity framework in view with multiple models

Question

I have created a view with multiple models (via ViewModel) to display data from multiple tables (i.e. billing address, shipping address, line items of an order). In my example, I would like to click the submit button to basically place an order, where only part of the information needs to be passed on and stored into a new table (orders), where let's say the billing address ID is referenced to keep it simple.

In a second step I will try to fetch the ID of the new row created in the orders table to update another (line item table). However, for some reason I don't even get beyond creating the record in the orders table - hence help is appreciated!

Below my controller - everything until ModelState validation works, after it breaks and gives me an 'object reference not set to an instance of an object' error...

// POST: /Shop/CreateOrder
[Authorize]
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult SubmitOrder(CreateOrderViewModel model)
{
// define variables
var userID = User.Identity.GetUserId();
DateTime nowUTC = DateTime.Now.ToUniversalTime();
DateTime nowLocal = DateTime.Now.ToLocalTime();
int NumberOfLineItems = DATADB.LineItemList.Where(x => x.OrderNumber == 0 && x.UserID == userID).Count();
decimal OrderAmount = DATADB.LineItemList.Where(x => x.OrderNumber == 0 && x.UserID == userID).Sum(x => x.TotalPrice);
if (ModelState.IsValid)
{
    var order = new Orders
    {
        UserID = userID,
        ShippingAddressID = model.ShippingAddressModel.ID,
        NumberOfLineItems = NumberOfLineItems,
        OrderAmount = OrderAmount,
        PaymentMethodID = model.PaymentMethodModel.ID,
        OrderDate = nowUTC,
        OrderLatitude = model.OrdersModel.OrderLatitude,
        OrderLongitude = model.OrdersModel.OrderLongitude,
        OrderLocation = model.OrdersModel.OrderLocation
    };
    DATADB.OrderList.Add(order);
    DATADB.SaveChanges();
    int orderID = order.ID;
    var lineItems = DATADB.LineItemList.Where(x => x.OrderNumber == 0 && x.UserID == userID);
    lineItems.ForEach(l => l.OrderNumber = orderID);
    DATADB.SaveChanges();
    return View("Home", "Home");
}
else
{
    return View(model);
}
}

The view model looks as follows:

public class CreateOrderViewModel
{
    public Orders OrdersModel { get; set; }
    public LineItems LineItemModel { get; set; }
    public IEnumerable<LineItems> LineItemListModel { get; set; }
    public ShippingAddressesViewModel ShippingAddressModel { get; set; }
    public ProfileInformationViewModel ProfileInformationModel { get; set; }
    public PaymentMethods PaymentMethodModel { get; set; }
}

... and the orders model like this:

public class Orders
{
    public int ID { get; set; }
    public string UserID { get; set; }
    public int ShippingAddressID { get; set; }
    public int NumberOfLineItems { get; set; }
    public int PaymentMethodID { get; set; }
    public decimal OrderAmount { get; set; }
    public decimal ShippingCost { get; set; }
    public DateTime OrderDate { get; set; }
    public string OrderLatitude { get; set; }
    public string OrderLongitude { get; set; }
    public string OrderLocation { get; set; }
}

And in which line the exception thrown? Usually the NRE thrown when you're using null reference - see [this issue](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it?rq=1) to get started debugging. — Tetsuya Yamamoto, Jan 07 '19 at 01:54
In addition to @Sahil Sharma answer, put DATADB.SaveChanges(); into try-catch block and see which exception do you get. There should be more information in there. — Matt, Jan 09 '19 at 13:43

Sahil Sharma · Answer 1 · 2019-01-09T13:14:25.693

Your view model CreateOrderViewModel contains multiple classes in it. In the following code, check for null-object scenarios:

if (ModelState.IsValid)
{
    //Check if model.ShippingAddressModel is empty
    //Check if model.PaymentMethodModel is empty
    //Check if model.OrdersModel is empty

    var order = new Orders
    {
        UserID = userID,
        ShippingAddressID = model?.ShippingAddressModel?.ID,
        NumberOfLineItems = NumberOfLineItems,
        OrderAmount = OrderAmount,
        PaymentMethodID = model?.PaymentMethodModel?.ID,
        OrderDate = nowUTC,
        OrderLatitude = model?.OrdersModel?.OrderLatitude,
        OrderLongitude = model?.OrdersModel?.OrderLongitude,
        OrderLocation = model?.OrdersModel?.OrderLocation
    };

   //
   //
}

create new record via entity framework in view with multiple models

1 Answers1