[英]How to configure a composite primary key containing a foreign key (EF Fluent API)
I have a one-to-many relationship between entities Curve and Point, defined as follows: 实体Curve和Point之间有一对多的关系,定义如下:
public class Curve
{
public Curve()
{
Points = new HashSet<Point>();
}
public int CurveId { get; set; }
public string Name { get; set; }
public virtual ICollection<Point> Points { get; set; }
}
And: 和:
public class Point
{
public int Point_Num { get; set; }
public int CurveId { get; set; }
public double XCoord { get; set; }
public double YCoord { get; set; }
public virtual Curve Curve { get; set; }
}
In my context class, I configure the keys and navigation properties as follows (note that the Point entity has a composite primary key): 在我的上下文类中,我按如下方式配置键和导航属性(请注意,Point实体具有复合主键):
protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
modelBuilder.Entity<Curve>()
.HasKey(c => c.CurveId);
modelBuilder.Entity<Point>()
.HasKey(p => new { p.Point_Num, p.CurveId });
modelBuilder.Entity<Point>()
.HasRequired(p => p.Curve)
.WithMany(c => c.Points)
.HasForeignKey(p => p.CurveId);
}
Somewhere else in the code, I populate the database: 在代码的其他地方,我填充数据库:
var curve = new Curve
{
Name = "curve 1"
};
var points = new List<Point>();
points.Add(new Point
{
XCoord = 1d,
YCoord = 1d,
});
points.Add(new Point
{
XCoord = 2d,
YCoord = 2d,
});
foreach (var point in points)
{
curve.Points.Add(point);
}
using (var dbCtxt = new MyDbContext())
{
try
{
dbCtxt.Curves.Add(curve);
dbCtxt.SaveChanges();
}
catch (Exception e)
{
Console.WriteLine(e.StackTrace);
}
}
An error is thrown when SaveChanges() is called "An error occurred while updating the entries." 调用SaveChanges()时发生错误“更新条目时发生错误”。
If I define Point_Num as the primary key of Point entity, all the entities update just fine. 如果我将Point_Num定义为Point实体的主键,则所有实体都会更新。 It seems like the problem comes from the fact that the composite primary key (Point_Num, CurveId) contains a foreign key (CurveId) 似乎问题来自复合主键(Point_Num,CurveId)包含外键(CurveId)的事实
I cannot get my head around this, there is clearly something I am missing. 我无法理解这一点,显然我缺少一些东西。 Any help will be much appreciated! 任何帮助都感激不尽!
So I have done what I should have done in the first place, which is creating my tables in SQL and using the Entity Data Model Wizard to generate my entities in C# (using "Code first from database") 所以我首先完成了我应该做的事情,即在SQL中创建我的表并使用实体数据模型向导在C#中生成我的实体(使用“数据库中的代码首先”)
Doing so, I noticed that EF generated the Point entity with the following "DatabaseGeneratedOption.None" data annotations on the composite primary key: 这样做,我注意到EF在复合主键上使用以下“DatabaseGeneratedOption.None”数据注释生成了Point实体:
public partial class Points
{
[Key]
[Column(Order = 0)]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Point_Num { get; set; }
[Key]
[Column(Order = 1)]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public int Curve_Id { get; set; }
...
public virtual Curve Curve { get; set; }
}
I impelemented this using Fluent API: 我使用Fluent API实现了这个目的:
modelBuilder.Entity<Point>().Property(p => p.PointId)
.HasDatabaseGeneratedOption(DatabaseGeneratedOption.None);
In the bit of code that populates the database, I create say, 2 different "Curve" entities: 在填充数据库的代码中,我创建了两个不同的“Curve”实体:
var curve1 = new Curve
{
Name = "curve 1"
};
var curve2 = new Curve
{
Name = "curve 2"
};
I then create "Point" entities specifying PointId and CurveId. 然后我创建指定PointId和CurveId的“Point”实体。 Eg let's say I want to add one point to each curve: 例如,假设我想为每条曲线添加一个点:
var points = new List<Point>();
points.Add(new Point
{
PointId = 1,
CurveId = 1,
XCoord = 1.2d,
YCoord = 3.1d,
});
points.Add(new Point
{
PointId = 1,
CurveId = 2,
XCoord = 0.5d,
YCoord = 0.75d,
});
When adding entities to the context, it is not sufficient to add the curve1 and curve2, I also need to add the list of points previously created, EF does not upload them automatically: 在向上下文添加实体时,仅添加curve1和curve2是不够的,我还需要添加先前创建的点列表,EF不会自动上传它们:
myContext.Points.AddRange(points);
myContext.Curves.Add(curve1);
myContext.Curves.Add(curve2);
myContext.SaveChanges();
It is not an elegant solution at all. 它根本不是一个优雅的解决方案。 I was hoping there would be a more straightforward way of doing this, but that solved my problem! 我希望有一种更简单的方法可以做到这一点,但这解决了我的问题! The database is updated correctly, all the keys and foreign keys are set up properly... 数据库正确更新,所有键和外键都正确设置...
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