Question

我有3个继承自 OwnableSpaceObject 的类，它通过ICollections为其子级提供2个导航属性。

从 OwnableSpaceObject ，我希望能够有一个像 AddChild 这样的类，它会将一个子类添加到ICollection并将其保存到数据库中。

这是 OwnableSpaceObject 基类：

public abstract class OwnableSpaceObject : SpaceObject
{
    public int? UserId { get; set; }
    public int? ResourcesId { get; set; }

    [ForeignKey("UserId")]
    public virtual UserProfile User { get; set; }

    [ForeignKey("ResourcesId")]
    public virtual Resources Resources { get; set; }

    public virtual ICollection<Structure> Structures { get; set; }
    public virtual ICollection<Ship> Ships { get; set; }
}

以下是我尝试使用的方法：

public Structure CheckOrAddChild(StructureType _structureType)
{
    using (ChronosContext db = new ChronosContext())
    {
        var structure = Structures != null ? Structures.FirstOrDefault(x =>   x.StructureTypeId == _structureType.Id) : null;
        if (structure == null)
        {
             Structure newStructure = new Structure(_structureType.Id);
             Structures.Add(newStructure); //this should add the Ship to the database and link it to the parent OwnableSpaceObject right? It errors out right here saying that Structures is null
             db.SaveChanges();

             structure = newStructure;
         }
         return structure;
    }
 }

类似地，一个重载的CheckOrAddChild用于添加Ships：

public virtual Ship CheckOrAddChild(ShipType _shipType)
        {
            using (ChronosContext db = new ChronosContext())
            {
                var ship = Ships != null ? Ships.FirstOrDefault(x => x.ShipTypeId == _shipType.Id) : null;
                if (ship == null)
                {
                    Ship newShip = new Ship(_shipType.Id);
                    Ships.Add(newShip); //this should add the Ship to the database and link it to the parent OwnableSpaceObject right? It errors out right here saying that Ships is null
                    db.SaveChanges();

                    ship = newShip;
                }
                return ship;
            }
        }

这基本上是Ships and Structures类的样子：

public class Ship
    {
        public int Id { get; set; }
        public int CurrentAmount { get; set; }
        public int BuildingAmount { get; set; }

        public int ShipTypeId { get; set; }

        [ForeignKey("ShipTypeId")]
        public virtual ShipType ShipType { get; set; }
}

Ship / Structure类没有OwnableSpaceObject的导航属性，因为它为我的所有Fleets / Asteroids / Planets创建了一个巨大的表，因为它们都继承自OwnableSpaceObject。我想让舰队/小行星/行星在表格中分开，但仍能将船只和结构连接到它们。目前，EF在Ships / Structures表中分别命名为“Asteroid_Id”，“Planet_Id”和“Fleet_Id”3列。我应该为每个这些创建一个导航属性并自己手动链接它们吗？我试图避免这种情况，以避免重复的代码。

任何人对此都有任何想法？我在过去的两天里一直在研究，我即将神经衰弱！

具有多个父类型的Entity Framework子级

0 个答案: