使用实体框架在一个表中包含2个外键 [英] 2 foreign keys in one table using entity framework

问题描述

我有3个课程

 事件，狗，结果
  因此必须表示我的结果类必须包含2个外键。 1表示事件，1表示狗。我对如何进行设置感到非常困惑。我已经在此方面获得了Som的帮助，希望有人能再次为我提供帮助。
 
 
 
现在这是我的课程：
 
 
 
公共类Dog 
 {
  public int DogId {get;组; } 
公共字符串Name {get;组; } 
 public int年龄{get;组; } 
 public bool已选中{get;组; } 
公共字符串DogImage {get;组; } 
 
 [ForeignKey（ Event）] 
 public int EventID {get;组; } 
 
 
公共虚拟ICollection< Result>结果{get;组; } 
 
公共虚拟事件Event {get;组; } 
} 
 
 public class Event 
 {
 public int EventId {get;组; } 
公共字符串EventName {get;组; } 
公共字符串EventLocation {get;组; } 
公共字符串EventType {get;组; } 
公共字符串EventDate {get;组; } 
 
公共虚拟ICollection< Dog>狗{组; } 
} 
 
公共类结果
 {
 public int ResultId {get;组; } 
 public int Track {get;组; } 
 public int服从{get;组; } 
 public int Protection {get;组; } 
 
 [ForeignKey（ Dog）] 
 public int DogId {get;组; } 
 
公共虚拟Dog Dog {get;组; } 
} 
  
感谢帮助！
 
 
 
编辑：
 
 
 
好的，这就是现在的样子。我应该告诉您，当我尝试对这些更新进行管理时，收到一个以结尾的错误：可能会导致循环或多个级联路径。指定ON DELETE NO ACTION或ON UPDATE NO ACTION，或修改其他FOREIGN KEY约束。 
 
 
 
我在dbcontext中添加了此方法，关心这个问题（我认为...）
 公共类EfdbContext：DbContext 
 {
 public DbSet< Event>活动{组; } 
 public DbSet< Dog>狗{组; } 
 public DbSet< Result>结果{get;组; } 
 
受保护的覆盖无效OnModelCreating（DbModelBuilder modelBuilder）
 {
 modelBuilder.Entity< Event>（）
 .HasRequired（c => c.Results）
 .WithMany（）
 .WillCascadeOnDelete（false）; 
} 
  
现在，当我尝试迁移时，出现此错误：
 
 
 ALTER TABLE语句与FOREIGN KEY约束 FK_dbo.Events_dbo.Results_Results_ResultId冲突。数据库 CloudDog.EFDB.EfdbContext的表 dbo.Results的 ResultId列中发生了冲突。 
这是我的班级现在的样子：
 
 
 
 
 
 公共课活动
 {
 public int EventId {组; } 
公共字符串EventName {get;组; } 
公共字符串EventLocation {get;组; } 
公共字符串EventType {get;组; } // Dropdown medtävlingar
 public string EventDate {get;组; } //选择器
 
公共虚拟ICollection< Dog>狗{组; } 
公共虚拟ICollection< Result>结果{get;组; } 
} 
 
公共类Dog 
 {
 public int DogId {get;组; } 
公共字符串Name {get;组; } 
 public int年龄{get;组; } 
 public bool已选中{get;组; } 
公共字符串DogImage {get;组; } 
 
 [ForeignKey（ Event）] 
 public int EventId {get;组; } 
 
公共虚拟ICollection< Merit>优点组; } 
公共虚拟ICollection< Result>结果{get;组; } 
 
公共虚拟事件Event {get;组; } 
} 
 
公共类结果
 {
 public int ResultId {get;组; } 
 public int Track {get;组; } 
 public int服从{get;组; } 
 public int Protection {get;组; } 
 
 [ForeignKey（ Dog）] 
 public int DogId {get;组; } 
公共虚拟Dog Dog {get;组; } 
 
 [ForeignKey（ Event）] 
 public int EventId {get;组; } 
公共虚拟事件Event {get;组; } 
} 
  
 
 
解决方案
在您的上一个问题，您并没有讲完整的故事。就其本身而言，解决方案是正确的。当两个类之间没有多对多的关联时，EF可以使用在类模型中仍然不可见的联结表对此建模。
 
 
 
但是现在您将更多信息添加到此联结表中。这意味着该表必须在类模型中表示为类，否则您将永远无法访问此信息。现在您的模型应该看起来像这样（简化为要点）：
 公共类Dog 
 {
 public int DogId {get;组; } 
公共虚拟ICollection< Result>结果{get;组; } 
} 
 
 public class Event 
 {
 public int EventId {get;组; } 
公共虚拟ICollection< Result>结果{get;组; } 
} 
 
公共类结果
 {
 public int ResultId {get;组; } 
 
 [ForeignKey（ Dog）] 
 public int DogId {get;组; } 
公共虚拟Dog Dog {get;组; } 
 
 [ForeignKey（ Event）] 
 public int EventId {get;组; } 
个公共虚拟狗事件{get;组; } 
} 
  
逻辑上，<$ c之间仍然存在多对多关联$ c> Dog 和 Event ，但是技术上将其实现为1-n-1关联。因此，通过添加信息，您牺牲了从 Dog  s到 Event  s以及之后的快捷访问。这是很常见的。我很少看到纯粹的多对多关联。人们迟早会开始存储有关该关联的信息。
 
 
 
现在，如果您想获取 Dog 的 Event  s，您必须编写一个更为复杂的查询：
 从d的狗
从d的r。结果
选择r。事件
  
 
I have three classes
Event, Dog, Result
Each dog can participate in many events and for each event he will get a score related to this specifik event.
Thus must mean that my result-class must contain 2 foreign keys. 1 that specifies the event and 1 that specifies the dog. I am very confused about how to set this up. I´ve been getting som help with this earlier and I hope someonen can help me again:

Here are my classes now:

public class Dog
    {
    public int DogId { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public bool Checked { get; set; }
    public string DogImage { get; set; }

    [ForeignKey("Event")]
    public int EventID { get; set; }


    public virtual ICollection<Result> Results { get; set; }

    public virtual Event Event { get; set; }
}

public class Event
    {
        public int EventId { get; set; }
        public string EventName { get; set; }
        public string EventLocation { get; set; }
        public string EventType { get; set; }
        public string EventDate { get; set; } 

        public virtual ICollection<Dog> Dogs { get; set; }
    }

 public class Result
    {
        public int ResultId { get; set; }
        public int Track { get; set; }
        public int Obedience { get; set; }
        public int Protection { get; set; }

        [ForeignKey("Dog")]
        public int DogId { get; set; }

        public virtual Dog Dog { get; set; }
    }
Help appreciated, thanks!

EDIT:

Ok, this is how it looks now. I should tellyou that when i tried to do a mgration with these updates I received an error ending with: may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.

I added this method in my dbcontext and it took care of that provblem(I Think...)
public class EfdbContext : DbContext
{
    public DbSet<Event> Events { get; set; }
    public DbSet<Dog> Dogs { get; set; }
    public DbSet<Result> Results { get; set; }

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    modelBuilder.Entity<Event>()
    .HasRequired(c => c.Results)
    .WithMany()
    .WillCascadeOnDelete(false);
} 
Now when I try to migrate I get this error:

  
The ALTER TABLE statement conflicted with the FOREIGN KEY constraint "FK_dbo.Events_dbo.Results_Results_ResultId". The conflict occurred in database "CloudDog.EFDB.EfdbContext", table "dbo.Results", column 'ResultId'.
  And this is how my classes look now:


public class Event
{
    public int EventId { get; set; }
    public string EventName { get; set; }
    public string EventLocation { get; set; }
    public string EventType { get; set; } //Dropdown med tävlingar
    public string EventDate { get; set; } //Picker

    public virtual ICollection<Dog> Dogs { get; set; }
    public virtual ICollection<Result> Results { get; set; }
}

public class Dog
{
    public int DogId { get; set; }
    public string Name { get; set; }
    public int Age { get; set; }
    public bool Checked { get; set; }
    public string DogImage { get; set; }

    [ForeignKey("Event")]
    public int EventId { get; set; }

    public virtual ICollection<Merit> Merits { get; set; }
    public virtual ICollection<Result> Results { get; set; }

    public virtual Event Event { get; set; }
}

 public class Result
{
    public int ResultId { get; set; }
    public int Track { get; set; }
    public int Obedience { get; set; }
    public int Protection { get; set; }

    [ForeignKey("Dog")]
    public int DogId { get; set; }
    public virtual Dog Dog { get; set; }

    [ForeignKey("Event")]
    public int EventId { get; set; }      
    public virtual Event Event { get; set; }
}

解决方案
In your previous question you didn't tell the whole story. In itself the solution was correct. When there is nothing but a many-to-many association between two classes then EF can model this by a junction table that remains invisible in the class model.

But now you add more information to this junction table. This means that the table must be represented as a class in the class model, otherwise you'll never be able to access this information. Now your model should look like this (reduced to the essentials):
public class Dog
{
    public int DogId { get; set; }
    public virtual ICollection<Result> Results { get; set; }
}

public class Event
{
    public int EventId { get; set; }
    public virtual ICollection<Result> Results { get; set; }
}

public class Result
{
    public int ResultId { get; set; }

    [ForeignKey("Dog")]
    public int DogId { get; set; }
    public virtual Dog Dog { get; set; }

    [ForeignKey("Event")]
    public int EventId { get; set; }
    public virtual Dog Event { get; set; }
}
Logically, there's still a many-to-many association between Dog and Event, but technically it is implemented as a 1-n-1 association. So by adding information you sacrifice the shortcut access from Dogs to Events and back. This is very common though. I don't often see pure many-to-many associations. Sooner or later people start storing information about the association.

Now if you want to fetch a Dog's Events, you'll have to write a somewhat more complicated query:
from d in Dogs
from r in d.Results
select r.Event


                        
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