C# EF导航属性不工作?
我有一门卡片课:C# EF导航属性不工作?,c#,.net,entity-framework,ef-code-first,C#,.net,Entity Framework,Ef Code First,我有一门卡片课: public class Card { public Card(){} [Key] [Required] public virtual int CardId { get; set; } [ForeignKey("StageId")] public virtual Stage Stage { get; set; } public int StageId { get; set; } } } 还有舞台课: publ
public class Card
{
public Card(){}
[Key]
[Required]
public virtual int CardId { get; set; }
[ForeignKey("StageId")]
public virtual Stage Stage { get; set; }
public int StageId { get; set; }
}
}
还有舞台课:
public class Stage
{
[Key]
public virtual int StageId { get; set; }
[DataMember(EmitDefaultValue = true)]
public string Name { get; set; }
public long Ticks { get; set; }
[NotMapped]
public TimeSpan Span
{
get { return TimeSpan.FromTicks(Ticks); }
}
// Make sure that these stages are generated accordingly
public static class Ids
{
// Zero
public const int One = 1;
// Ten Seconds
public const int Two = 2;
// One Minute
}
}
在我的存储库服务中,我有一个AddCard方法:
public Card AddCard(Card card)
{
int parentId = 0;
Set parentSet = null;
if (card.ParentSetId.HasValue)
{
parentId = card.ParentSetId.Value;
parentSet = GetSet(parentId);
}
card.ParentSet = parentSet;
card.ParentSetId = parentSet.SetId;
card.StageId = Stage.Ids.One; // Set Id here with hopes of getting card.Stage to resolve as a nav property
_db.Cards.Add(card);
SaveChanges();
return card;
}
但由于某些原因,我所有的卡的Card.Stage值都是空的,其中Card.StageId总是某个整数。我正在尝试让导航属性工作,这样我就可以通过一张卡访问舞台的属性
我做错了什么
更新:
当我尝试通过测试访问属性时,该属性为null。首先,我创建卡(在我的测试代码中):
然后我将其发送到我的Dto服务(也在测试代码中):
CardDto类别:
public class CardDto
{
public CardDto(){}
public CardDto(Card card)
{
CardId = card.CardId;
Stage = card.Stage.Name; // Fails here on its way back - creating the initial DTO works
Details = card.Details;
}
[Key]
[DataMember(EmitDefaultValue = true)]
public int CardId { get; set; }
[DataMember(EmitDefaultValue = true)]
public string Stage { get; set; }
[DataMember(IsRequired = false)]
public string Details { get; set; }
public Card ToEntity()
{
var newCard = new Card
{
CardId = CardId,
Details = Details,
};
return newCard;
}
_服务是DTO服务:
public CardDto AddCard(CardDto card)
{
return new CardDto(_repository.AddCard(card.ToEntity()));
}
\u存储库
代码在上面
这在_repository调用过程中一直有效,但如果调试_repository.AddCard方法,则在调用SaveChanges()之后,StageId有一个值,但Stage没有
该卡将沿着链向上传递,直到应该再次转换为Dto为止,由于空阶段,该卡将失败
奇怪的是,这段代码在测试之外工作——如果我使用客户机点击AddCard,我会得到一张没有任何错误的卡 要使延迟加载正常工作,您需要创建一个代理。如果你正在加载卡片 EF您将自动收到一个包裹在代理对象中的对象。您可以在这里做两件事
1.要使用延迟加载,可以创建如下代理
public Card AddCard(Card card)
{
var cardProxy= _db.Cards.Create();
//and copy all values from card to cardProxy here..
int parentId = 0;
Set parentSet = null;
if (cardProxy.ParentSetId.HasValue)
{
parentId = cardProxy.ParentSetId.Value;
parentSet = GetSet(parentId);
}
cardProxy.ParentSet = parentSet;
cardProxy.ParentSetId = parentSet.SetId;
cardProxy.StageId = Stage.Ids.One; // Set Id here with hopes of getting card.Stage to resolve as a nav property
SaveChanges();
return cardProxy;
}
card.ParentSet = parentSet;
card.ParentSetId = parentSet.SetId;
card.StageId = Stage.Ids.One; // Set Id here with hopes of getting card.Stage to resolve as a nav property
_db.Cards.Add(card);
SaveChanges();
context.Entry(card).Reference(p => p.Stage).Load();//load stage here
return card;
}
您是否检查了数据库数据?它是否具有卡的StageId值?好的,那么您是否启用了延迟加载或使用了Include?如何检索阶段?我没有禁用它,也没有禁用Include。阶段是通过上面代码中所示的ID访问的。我误解了您的问题吗?您能告诉我阶段所在的代码吗当你访问它时为空?@Jayantha哦!是的,现在发布非常感谢。我刚刚在你的博客上发布了一些东西。
public Card AddCard(Card card)
{
var cardProxy= _db.Cards.Create();
//and copy all values from card to cardProxy here..
int parentId = 0;
Set parentSet = null;
if (cardProxy.ParentSetId.HasValue)
{
parentId = cardProxy.ParentSetId.Value;
parentSet = GetSet(parentId);
}
cardProxy.ParentSet = parentSet;
cardProxy.ParentSetId = parentSet.SetId;
cardProxy.StageId = Stage.Ids.One; // Set Id here with hopes of getting card.Stage to resolve as a nav property
SaveChanges();
return cardProxy;
}
card.ParentSet = parentSet;
card.ParentSetId = parentSet.SetId;
card.StageId = Stage.Ids.One; // Set Id here with hopes of getting card.Stage to resolve as a nav property
_db.Cards.Add(card);
SaveChanges();
context.Entry(card).Reference(p => p.Stage).Load();//load stage here
return card;
}