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c# - 使用多个模型通过实体框架创建新记录

问题描述

我创建了一个包含多个模型的视图（通过 ViewModel）来显示来自多个表的数据（即帐单地址、送货地址、订单的行项目）。在我的示例中，我想单击提交按钮以基本上下订单，其中只需要传递部分信息并将其存储到新表（订单）中，假设账单地址 ID 被引用以保留很简单。

在第二步中，我将尝试获取在订单表中创建的新行的 ID 以更新另一个（行项目表）。但是，出于某种原因，我什至无法在订单表中创建记录 - 因此感谢您的帮助！

在我的控制器下方 - 在 ModelState 验证工作之前的所有内容，在它中断并给我一个“对象引用未设置为对象的实例”错误之后......

// 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);
}
}

视图模型如下所示：

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; }
}

...和这样的订单模型：

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; }
}

标签： c#asp.net-mvcentity-framework

解决方案

您的视图模型CreateOrderViewModel中包含多个类。在以下代码中，检查空对象方案：

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
    };

   //
   //
}

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