[英]Code First entity framework and foreign keys
Imagine I have a database created by code first that looks like this. 想象一下,我有一个由代码创建的数据库,看起来像这样。
Movie (table)
ID int PK
MoveiName nvarchar(100)
Actor (table)
ID int PK
ActorName nvarchar(100)
Movie_ID int FK
These are the models I would have used, obviously not exactly like this but you'll get my point. 这些是我会使用的模型,显然不完全是这样,但你会明白我的观点。
class Movie
{
int ID{get;set;}
string MovieName {get;set;}
List<Actor> Actors {get;set}
}
class Actor
{
int ID{get;set}
string Actorname{get;set}
Movie Movie{get;set;}
int Move_ID{get;set;}
}
Database first enables me to query the movie from an actor but also lets me set the forgien key property of the actor to update the database. 数据库首先使我能够从一个actor查询电影,但也允许我设置actor的forgien键属性来更新数据库。 I cant do this in code first because the foreign key isnt in the model only the object. 我不能在代码中首先执行此操作,因为外键在模型中不仅仅是对象。 I prefer not to get the Movie object and set the property, if i know the id of my movie I'd rather just set the foreign key without the call to get the movie. 我不想获取Movie对象并设置属性,如果我知道我的电影的ID我宁愿只设置外键而没有调用来获取电影。
Make sense? 合理? lol 大声笑
I want to use codefirst and entity migrations but i want the same ability as database first to set a foreign key on an object. 我想使用codefirst和实体迁移,但我想要与数据库相同的能力首先在对象上设置外键。
Cheers for the help :-D 干杯的帮助:-D
First change your code to this 首先将代码更改为此
public class Movie
{
int ID{ get; set; }
string MovieName {get; set; }
List<Actor> Actors {get; set; }
}
public class Actor
{
int ID{get;set}
string ActorName{ get; set }
Movie Movie{ get; set; }
int MovieID{ get; set; }
}
By convention EF will know that MovieID
is the foreign key to Movie
按照惯例, EF将知道MovieID
是Movie
的外键
Then change Actor
code to this: 然后将Actor
代码更改为:
public class Actor
{
int ID{get;set}
string ActorName{ get; set; }
Movie Movies{ get; set; }
}
Actors appear in many movies. 演员出现在很多电影中。 Movies have many actors.... :-) 电影有很多演员...... :-)
But going back to your one-to-many where an actor only appears in one movie - if you really want the foreign key to be Move_ID
then add a data annotation : 但回到你的一对多,其中演员只出现在一部电影中 - 如果你真的想要外键是Move_ID
那么添加一个数据注释 :
[ForeignKey("Move_ID")]
Movie Movie{ get; set; }
Or configure it using FluentAPI
或者使用FluentAPI
配置
modelBuilder.Entity<Actor>()
.HasRequired(c => c.Movie)
.WithMany(d => d.Actors)
.HasForeignKey(c => c.Move_ID);
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