Linq 嵌套关系和 DTO

Question

我正在从 Oracle 数据库获取数据并创建一个 API 供内部使用。一些类是（为简洁起见缩短）：

CustomerOrderTab

    Public partial class CustomerOrderTab
    Public string OrderNo { get; set; }
    [ForeignKey("CustomerMV")]
    public string CustomerNo { get; set; }
    public List<CustomerOrderLineTab> CustomerOrderLines { get; set; }
    public List<CustomerOrderChargeTab> CustomerOrderCharge { get; set; }
    public List<ShipmentOrderLineTab> ShipmentOrderLines { get; set; }
    public CustomerMV CustomerMV { get; set; }

CustomerOrderDTO

    Public class OrderDTO
    public string OrderNo { get; set; }
    public string CustomerName { get; set; }
    public List<OrderLinesDTO> OrderLines { get; set; }
    public List<OrderChargesDTO> OrderCharges { get; set; }
    public List<ShipmentOrderLinesDTO> ShipmentOrderLines { get; set; }

ShipmentOrderLineTab

    public partial class ShipmentOrderLineTab
    public decimal ShipmentId { get; set; }
    [ForeignKey("CustomerOrderTab")]
    public string OrderNo { get; set; }
    public ShipmentTab Shipment { get; set; }

ShipmentOrderLineDTO

    public class ShipmentOrderLinesDTO
    public decimal ShipmentId { get; set; }
    public string OrderNo { get; set; }
    public ShipmentTab MyShipment { get; set; }

发货选项卡

    public partial class ShipmentTab
    [ForeignKey("ShipmentOrderLineTab")]
    public decimal ShipmentId { get; set; }
    public string ShipperAddress1 { get; set; }
    public string ShipperAddress2 { get; set; }
    public List<ShipmentHandlingUnitTab> ShipmentHandlingUnits { get; set; }

发货DTO

    public class ShipmentDTO
    public decimal ShipmentId { get; set; }
    public string ShipViaCode { get; set; }
    public string ShipmentPayer { get; set; }
    public List<ShipmentHandlingUnitDTO> ShipmentHandlingUnitDTOs { get; set; }

这个作品：

    var orderLines = from o in _context.CustomerOrderTab
                         .Where(o => o.OrderNo == orderno)
                         select new OrderDTO()
                         {
                             OrderNo = o.OrderNo,
                             CustomerName = o.CustomerMV.CustomerName,

    This is a child of the order     ShipmentOrderLines = o.ShipmentOrderLines
    This works          .Select(ob => new ShipmentOrderLinesDTO
                             {
                                 ShipmentId = ob.ShipmentId,
                                 OrderNo = ob.OrderNo,
                                 MyShipment = ob.Shipment
    Adding this does not work         .Select(y => new ShipmentDTO
    The error says that ShipmentTab
     Doesn’t have a definition for Select    {
                                        }
                             }).ToList()

Shipment 是 ShipmentOrderLine 的子项（每行只有一个货件）

ShipmentOrderLine 是 CustomerOrder 的子项（每个订单可以有很多行）

我认为问题是每行只有一个货件，但我已经尝试了很多东西，但无法将其映射到我的 DTO。

Answer 1

修复您的模型：

ShipmentOrderLineDTO

public class ShipmentOrderLinesDTO
public decimal ShipmentId { get; set; }
public string OrderNo { get; set; }
public ShipmentDTO MyShipment { get; set; }

Select仅用于投射一个集合。对于非集合，您只需创建一个新对象...

var orderLines = _context.CustomerOrderTab
  .Where(o => o.OrderNo == orderno)
  .Select(o => new OrderDTO {
    OrderNo = o.OrderNo,
    CustomerName = o.CustomerMV.CustomerName,
    ShipmentOrderLines = o.ShipmentOrderLines
      .Select(ob => new ShipmentOrderLinesDTO {
        ShipmentId = ob.ShipmentId,
        OrderNo = ob.OrderNo,
        MyShipment = new ShipmentDTO {
          ShipmentId = ob.Shipment.ShipmentId,
          ...
          ShipmentHandlingUnits = ob.Shipment.ShipmentHandlingUnits
            .Select(shu=> new ShipmentHandlingUnitDTO {
              ...
            }).ToList()
        }
      }
    }).ToList()

话虽如此，我通常在我的数据模型 classes 上有映射扩展方法，它允许这样的事情：

var orderLines = _context.CustomerOrderTab
  .Where(o=>o.OrderNo == orderno)
  .Select(o=> o.ToDto());

示例class：

public static class CustomerOrderTabExtensions {
  public static CustomerOrderDto ToDto(this CustomerOrderTab cot) {
    return new CustomerOrderDto {
      OrderNo = cot.OrderNo,
      ...
      OrderLines = cot.CustomerOrderLines
        .Select(col=>col.ToDto())
        .ToList()
    }
  }
}

或使用Automapper.

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