实体框架中的一对零或一种关系

Question

I have 2 standard entities :

Group :

[Table("CONTROL_GROUP", Schema = "CONTROL")]
public partial class Group
{
    [Key, DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Required]
    [Column("ID")]
    public decimal Id { get; set; }

    [Required]
    [Column("NAME")]
    [MaxLength(200)]
    public string Name { get; set; }

    public virtual GroupMetier GroupMetier { get; set; }
}

GroupMetier:

[Table("CONTROL_GROUP_METIER", Schema = "CONTROL")]
public partial class GroupMetier
{
    [Key]
    [Required]
    [Column("GROUP_ID")]
    public int GroupId { get; set; }

    [Required]
    [Column("NAME")]
    [MaxLength(200)]
    public string Name { get; set; }

    public virtual Group Group { get; set; }
}

In my model builder, I defined the relashionship as follow :

// GroupMetier 0..1 <-> 1 Group
modelBuilder.Entity<GroupMetier>()
    .HasRequired<Group>(gm => gm.Group)
    .WithOptional(g => g.GroupMetier)

However, on execution, when I try to retrive the groups with this linq :

_context.Groups.Where(item => item.GroupMetier != null)

The generated sql failed to execute :

SELECT 
    "Extent3"."GROUP_ID" AS "GROUP_ID", 
    "Extent1"."ID" AS "ID", 
    "Extent1"."NAME" AS "NAME", 
    "Extent2"."GROUP_ID" AS "GROUP_ID1"
FROM   "CONTROL"."CONTROL_GROUP" "Extent1"
    LEFT OUTER JOIN "CONTROL"."CONTROL_GROUP_METIER" "Extent2" ON "Extent1"."ID" = "Extent2"."GroupId"
    INNER JOIN "CONTROL"."CONTROL_GROUP_METIER" "Extent3" ON "Extent1"."ID" = "Extent3"."GroupId"
WHERE (1 = 1)

The problem come obviously from entity trying to join on an non existing "Extent2"."GroupId" column instead of the right "Extent2"."GROUP_ID"

Have I failed to declare something somewhere for this relashionship to work ?

Edit : As requested, the CONTROL.CONTROL_GROUP_METIER table :

CREATE TABLE CONTROL.CONTROL_GROUP_METIER
(
  GROUP_ID  INTEGER                             NOT NULL,
  NAME      VARCHAR2(200 CHAR)                  NOT NULL
)
TABLESPACE CONTROL_DATA
RESULT_CACHE (MODE DEFAULT)
PCTUSED    0
PCTFREE    10
INITRANS   1
MAXTRANS   255
STORAGE    (
            INITIAL          64K
            NEXT             1M
            MAXSIZE          UNLIMITED
            MINEXTENTS       1
            MAXEXTENTS       UNLIMITED
            PCTINCREASE      0
            BUFFER_POOL      DEFAULT
            FLASH_CACHE      DEFAULT
            CELL_FLASH_CACHE DEFAULT
           )
LOGGING 
NOCOMPRESS 
NOCACHE
NOPARALLEL
MONITORING;


CREATE UNIQUE INDEX CONTROL.CONTROL_GROUP_METIER_PK ON CONTROL.CONTROL_GROUP_METIER
(GROUP_ID)
LOGGING
TABLESPACE CONTROL_DATA
PCTFREE    10
INITRANS   2
MAXTRANS   255
STORAGE    (
            INITIAL          64K
            NEXT             1M
            MAXSIZE          UNLIMITED
            MINEXTENTS       1
            MAXEXTENTS       UNLIMITED
            PCTINCREASE      0
            BUFFER_POOL      DEFAULT
            FLASH_CACHE      DEFAULT
            CELL_FLASH_CACHE DEFAULT
           )
NOPARALLEL;


ALTER TABLE CONTROL.CONTROL_GROUP_METIER ADD (
  CONSTRAINT CONTROL_GROUP_METIER_PK
  PRIMARY KEY
  (GROUP_ID)
  USING INDEX CONTROL.CONTROL_GROUP_METIER_PK
  ENABLE VALIDATE);

ALTER TABLE CONTROL.CONTROL_GROUP_METIER ADD (
  CONSTRAINT CONTROL_GROUP_METIER_R01 
  FOREIGN KEY (GROUP_ID) 
  REFERENCES CONTROL.CONTROL_GROUP (ID)
  ENABLE VALIDATE);

Answer 1

Have I failed to declare something somewhere for this relashionship to work ?

Your configuration is just fine for so called Shared Primary Key Association and normally would produce a migration like this (just to test the mapping):

CreateTable(
    "CONTROL.CONTROL_GROUP_METIER",
    c => new
        {
            GROUP_ID = c.Int(nullable: false),
            NAME = c.String(nullable: false, maxLength: 200),
        })
    .PrimaryKey(t => t.GROUP_ID)
    .ForeignKey("CONTROL.CONTROL_GROUP", t => t.GROUP_ID)
    .Index(t => t.GROUP_ID);

However, it actually produces this:

CreateTable(
    "CONTROL.CONTROL_GROUP_METIER",
    c => new
        {
            GROUP_ID = c.Int(nullable: false, identity: true),
            NAME = c.String(nullable: false, maxLength: 200),
            Group_Id = c.Decimal(nullable: false, precision: 18, scale: 2),
        })
    .PrimaryKey(t => t.GROUP_ID)
    .ForeignKey("CONTROL.CONTROL_GROUP", t => t.Group_Id)
    .Index(t => t.Group_Id);

which as you can see is not what you want.

Why is that? To better understand, let apply the explicit ForeignKey attribute to the Group property:

[ForeignKey("GroupId")]
public virtual Group Group { get; set; }

Now the migration fails with the following error:

GroupMetier_Group_Target_GroupMetier_Group_Source: : The types of all properties in the Dependent Role of a referential constraint must be the same as the corresponding property types in the Principal Role. The type of property 'GroupId' on entity 'GroupMetier' does not match the type of property 'Id' on entity 'Group' in the referential constraint 'GroupMetier_Group'.

So the problem is that the Group.Id property type is decimal and GroupMetier.GroupId property type is int , in which case EF fails to recognize the relationship and tries to use One-to-One Foreign Key Association which of course doesn't match your database model.

How to fix it? It's hard to tell, but you somehow should make both properties int or decimal .

Answer 2

Did you try the ForeignKey annotation?

[ForeignKey("GROUP_ID")]
public virtual Group Group { get; set; }

Answer 3

in fluent API

modelBuilder.Entity<GroupMetier>()
.HasRequired<Group>(gm => gm.Group)
.WithOptional(g => g.GroupMetier)
.Map(g => g.MapKey("GROUP_ID"));