为什么EF代码优先生成多余的外键列？ [英] Why is EF code-first generating an extraneous foreign key column?

问题描述

我使用实体框架代码优先自动创建我的数据库架构，我的实体之一是这样的：

I'm using entity framework code-first to create my database schema automatically, and one of my entities looks like this:

public class AssessmentsCaseStudies {
    #region Persisted fields
    [Required]
    [Key, Column(Order=0)]
    [ForeignKey("Assessment")]
    public int AssessmentId { get; set; }

    [Required]
    [Key, Column(Order=1)]
    [ForeignKey("CaseStudy")]
    public int CaseStudyId { get; set; }

    [Required]
    public int Score { get; set; }

    [ForeignKey("Follows")]
    public int? FollowsCaseStudyId { get; set; }
    #endregion

    #region Navigation properties
    public virtual Assessment Assessment { get; set; }
    public virtual CaseStudy CaseStudy { get; set; }
    public virtual CaseStudy Follows { get; set; }
    #endregion
}

当EF自动生成我的数据库，它生成一个表具有以下的列：

When EF auto-generates my database, it generates a table with the following columns:

AssessmentId (PK, FK, int, not null)
CaseStudyId (PK, FK, int, not null)
Score (int, not null)
FollowsCaseStudyId (FK, int, null)
CaseStudy_CaseStudyId (FK, int, null)

这是所有罚款从 CaseStudy_CaseStudyId 列分开。为什么说已经产生？这是什么呢？我怎样才能阻止正在生成的呢？我怀疑是EF可以不再自动匹配的案例研究 的ICollection< AssessmentsCaseStudies> 与 CaseStudyId 列，因此它会创建自己列两个为导航属性链接在一起。

This is all fine apart from the CaseStudy_CaseStudyId column. Why has that been generated? What is it for? How can I stop it being generated? My suspicion is that EF can no longer automatically match up CaseStudy's ICollection<AssessmentsCaseStudies> with the CaseStudyId column, so it creates its own column to link the two together for that navigation property.

推荐答案

由于某些原因，Slauma的 InverseProperty 属性的建议没有工作。是什么做的工作是我指定的 AssessmentsCaseStudies 两个案例研究导航性能之间的关系，以及案例研究实体，通过在我的数据库上下文的 OnModelCreating 方法流利的API：

For some reason, Slauma's InverseProperty attribute suggestion didn't work. What did work was me specifying the relationship between the two CaseStudy navigation properties in AssessmentsCaseStudies, and the CaseStudy entity, via the Fluent API in my database context's OnModelCreating method:

modelBuilder.Entity<AssessmentsCaseStudies>()
    .HasRequired(acs => acs.CaseStudy)
    .WithMany(cs => cs.AssessmentsCaseStudies)
    .HasForeignKey(acs => acs.CaseStudyId)
    .WillCascadeOnDelete(false);

modelBuilder.Entity<AssessmentsCaseStudies>()
    .HasOptional(acs => acs.Follows)
    .WithMany()  // No reverse navigation property
    .HasForeignKey(acs => acs.FollowsCaseStudy)
    .WillCascadeOnDelete(false);

在了加，这是生成的，当我迁移代码添加迁移不再尝试添加 CaseStudy_CaseStudyId 列，我只是得到了 FollowsCaseStudyId 栏加入其中，相应的外键关系。

Once that's added, the migration code that's generated when I Add-Migration no longer tries to add the CaseStudy_CaseStudyId column and I just get the FollowsCaseStudyId column added, with the appropriate foreign key relationship.

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