Question

我有两个POCO条款清单和电子书详情

如何将数据检索为Inventory to =＆gt;很多很多

public class Inventory
{
    // This determine the One to Many RelationShip
    public Inventory()
    {
        this.Lots = new HashSet<Lot>();
    }

    [ScaffoldColumn(false)]
    public int Id { get; set; }
    [Required]
    public string ItemID { get; set; }
    public string Description { get; set; }
    public Nullable<DateTime> CreateDate { get; set; }
    public string CreateUser { get; set; }
    public decimal LastCost { get; set; }
    public bool MonitorLevel { get; set; }
    public short MinLevel { get; set; }
    public short MaxLevel { get; set; }
    public string GTIN { get; set; }
    public decimal Weight { get; set; }
    public string UOM { get; set; }

    // Navigation Property
    public virtual ICollection<Lot> Lots { get; set; }
}

public class Lot
{
    public int Id { get; set; }
    public Nullable<DateTime> CreateDate { get; set; }
    public string CreateUser { get; set; }
    public Nullable<DateTime> ExpDate { get; set; }
    public string LotSerial { get; set; }

    public virtual Inventory Inventory { get; set; }
}

我试试这个，但转换类型有错误

public class InventoryController : ApiController
{
    private FarmStoreContext db = new FarmStoreContext();

    // Project Inventory to inventory DTOs.

    private IQueryable<InventoryDTO> MapInventories()
    {
        return from i in db.Inventories
               select new InventoryDTO() { Id = i.Id, Description = i.Description, ItemID = i.ItemID, GTIN = i.GTIN, LastCost = i.LastCost, Weight = i.Weight, UOM = i.UOM};
    }

    public IEnumerable<InventoryDTO> GetInventories()
    {
        return MapInventories().AsEnumerable();
    }

    public InventoryDTO GetInventory(int Id)
    {
        Inventory inventory = db.Inventories;// <== Error - Here can not implicity convert type System.Data.Entiry.Dbset<....Models.Inventory> To ....Models.Inventory

        //var inventory = (from i in MapInventories()
          //               where i.Id == Id
            //             select i).FirstOrDefault();

        if (inventory == null)
        {
            throw new HttpResponseException(
                Request.CreateResponse(HttpStatusCode.NotFound));
        }

        return new InventoryDTO()
        {
            DetaislLots = from d in inventory.Lots
                          select new InventoryDTO.DetaislLot()
                          {
                              LotSerial = d.LotSerial,
                              LIFOdate = d.LIFOdate,
                              QtyOriginal = d.QtyOriginal,
                              QtyAllocated = d.QtyAllocated,
                              QtyOnHand = d.QtyOnHand,
                              QtyAvailable = d.QtyAvailable,
                              Status = d.Status,
                              LineComment = d.LineComment,
                              UnitCost = d.UnitCost,
                              ReceiptDate = d.ReceiptDate
                          }
        };
    }

    protected override void Dispose(bool disposing)
    {
        db.Dispose();
        base.Dispose(disposing);
    }
}

Answer 1

db.Inventories是一个DbSet<Inventory>，它是一个集合，而您期待一个Inventory。您必须执行返回单个Inventory的查询。尝试：

Inventory inventory = db.Inventories.FirstOrDefault(i => i.Id == Id);

您在该行下方的评论中基本上都有此查询。您可以使用Lots上的导航属性Inventory来获取相关的Lot个对象：

List<Lot> lots = inventory.Lots.ToList();

实体框架一对多：不能隐式转换

1 个答案: