c# - EF Code First，同一对象的两个导航属性

Question

我正在使用 EF Code First 查询和创建数据库。我的一个实体(关系)对同一个实体(事件)有两个导航属性。我的问题是，如果我使用 EF 创建数据库模式，它将创建四个外键列和约束，而不是两个。

相关代码部分如下:

事件类:

public class Activity {
    public virtual ICollection<Relationship> Successors { get; set; }
    public virtual ICollection<Relationship> Predecessors { get; set; }
}

关系类:

public class Relationship {
    public virtual Activity Activity1 { get; set; }
    public int Activity1_ID { get; set; }
    public virtual Activity Activity2 { get; set; }
    public int Activity2_ID { get; set; }
}

关系映射类:

this.HasRequired(t => t.Activity1)
  .WithMany(t => t.Predecessors)
  .HasForeignKey(m => m.Activity1_ID)
  .WillCascadeOnDelete(false);
this.HasRequired(t => t.Activity2)
  .WithMany(t => t.Successors)
  .HasForeignKey(m => m.Activity2_ID)
  .WillCascadeOnDelete(false);

数据库结构:

有没有办法阻止创建最后两列？

Answer 1

这应该只为您创建 2 个外键列。

public class Activity
{
    public int Id { set; get; }
    public virtual ICollection<Relationship> Successors { get; set; }
    public virtual ICollection<Relationship> Predecessors { get; set; }
}
public class Relationship
{
    public int Id { set; get; }
    public virtual Activity Activity1 { get; set; }
    public int Activity1_ID { get; set; }
    public virtual Activity Activity2 { get; set; }
    public int Activity2_ID { get; set; }
}

还有我在 OnModelCreating 上指定关系/FK 性质的 DbContext 类。

public class MyDb: DbContext
{
    public MyDb():base("EfDbContext")
    {           
    }
    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {            
        modelBuilder.Entity<Relationship>()
            .HasRequired(f => f.Activity1)
            .WithMany(f => f.Predecessors)
            .HasForeignKey(g => g.Activity1_ID)
            .WillCascadeOnDelete(false);

        modelBuilder.Entity<Relationship>().
             HasRequired(f => f.Activity2)
            .WithMany(f => f.Successors)
            .HasForeignKey(g => g.Activity2_ID)
            .WillCascadeOnDelete(false);
    }
}