c# - EF Core中的可空拥有类型

我的情况下，我想存储一个地址，但它必须是可选的。

我的映射如下所示:

map.OwnsOne(x => x.Address, cb => cb.OwnsOne(l => l.Location));

但是当将我的DbContext的地址设置为空iam时出现此错误:



然后，我从构造函数实例化了Address和Location，现在可以保存实体。但是，当再次获取数据时，我也得到了一个实例化的地址，我真的想要一个空值。

不能创建可为空的拥有类型吗？

最佳答案

从EF Core 3开始，这已经成为可能。



Sample Code:

static void Main(string[] args)
{
  using (var context = new OwnedEntityContext())
  {
    context.Add(new DetailedOrder
    {
      Status = OrderStatus.Pending,
      OrderDetails = new OrderDetails
      {
        ShippingAddress = new StreetAddress
        {
          City = "London",
          Street = "221 B Baker St"
        }
        //testing 3.0: "Yes, all dependents are now optional"
        //reference: https://github.com/aspnet/EntityFrameworkCore/issues/9005#issuecomment-477741082
        //NULL Owned Type Testing
        //BillingAddress = new StreetAddress
        //{
        //    City = "New York",
        //    Street = "11 Wall Street"
        //}
      }
    });
    context.SaveChanges();
  }
  //read test
  using (var context = new OwnedEntityContext())
  {
    #region DetailedOrderQuery
    var order = context.DetailedOrders.First(o => o.Status == OrderStatus.Pending);
    Console.Write("NULL Owned Type Test, Is Billing Address NULL?");
    //PRINTS FALSE
    Console.WriteLine($"{order.OrderDetails.BillingAddress == null}");
    #endregion
  }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    #region OwnsOneNested
    modelBuilder.Entity<DetailedOrder>().OwnsOne(p => p.OrderDetails, od =>
    {
        od.OwnsOne(c => c.BillingAddress);
        od.OwnsOne(c => c.ShippingAddress);
    });
    #endregion

    #region OwnsOneTable
    modelBuilder.Entity<DetailedOrder>().OwnsOne(p => p.OrderDetails, od =>
    {
        od.OwnsOne(c => c.BillingAddress);
        od.OwnsOne(c => c.ShippingAddress);
        od.ToTable("OrderDetails");
        //Exception message:Microsoft.Data.SqlClient.SqlException:
        //'Cascading foreign key 'FK_OrderDetails_DetailedOrders_OrderId' cannot
        //be created where the referencing column 'OrderDetails.OrderId' is an identity column.
        //Could not create constraint or index. See previous errors.'
        //3.0 bug: https://github.com/aspnet/EntityFrameworkCore/issues/17448#issuecomment-525444101
        //fixed in 3.1: https://github.com/aspnet/EntityFrameworkCore/pull/17458
        od.Property("OrderId")
            .ValueGeneratedNever();
    });
    #endregion
}