如何解决C# Entity Framework Code-First - 如何仅使用外键的 id 添加带有外键的行?
public class Notifications
{
[Key]
public int ID { get; set; }
public virtual ClientDetails Client { get; set; }
public virtual NotificationTypes NotificationType { get; set; }
public virtual NotificationFreqs Frequency { get; set; }
public virtual NotificationStatus Status { get; set; }
public DateTime SendDate { get; set; }
public DateTime? SentDate { get; set; }
public DateTime QueueDate { get; set; }
}
public class NotificationFreqs
{
[Key]
public int ID { get; set; }
[MaxLength(25)]
public string Name { get; set; }
}
public class NotificationStatus
{
[Key]
public int ID { get; set; }
[MaxLength(25)]
public string Status { get; set; }
}
添加新通知时,最有效的说 notification.status = 1
方式是什么?
我是否每次都必须查询数据库才能获得可用列表?
var notification = new Notifications();
var notificationType = db.NotificationTypes.FirstOrDefault(n => n.ID == notificationTypeId);
var notificationFreq = db.NotificationFreqs.FirstOrDefault(n => n.Name == setting.Value);
notification.NotificationType = notificationType; // Works
notification.Frequency = notificationFreq; // Works
notification.Status = new NotificationStatus { ID = 1 }; // ObvIoUsly doesn't work
我觉得多次访问数据库效率低下,但我确实希望这些值标准化并在数据库中。
有什么建议吗,或者我的做法是 NotificationType
和 Frequency
的唯一方法?
谢谢!
解决方法
你必须修复你的课程。添加 ID 字段:
public class Notifications
{
[Key]
public int ID { get; set; }
public virtual ClientDetails Client { get; set; }
[ForeignKey("NotificationType")]
public int? Type_ID { get; set; }
public virtual NotificationTypes NotificationType { get; set; }
[ForeignKey("Frequency")]
public int? Frequency_ID { get; set; }
public virtual NotificationFreqs Frequency { get; set; }
[ForeignKey("Status")]
public int? Status_ID { get; set; }
public virtual NotificationStatus Status { get; set; }
public DateTime SendDate { get; set; }
public DateTime? SentDate { get; set; }
public DateTime QueueDate { get; set; }
}
在这种情况下:
notification.Type_ID = notificationTypeId;
notification.Frequency_ID = notificationFreq.ID;
notification.Status_ID = 1
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