实体框架中相同类型的多个外键

Question

我有 Issue 实体有 2 个字段作为 FK 到 User 实体，如下所示。尽管我正确配置了属性以防止创建额外的Xxx_Id 字段而不是PropertyNameId，但除了PropertyNameId 字段之外，表中还创建了一个Xxx_Id 字段。在此示例中，除了 AssigneeId 和 ReporterId 字段之外，Issue 表中还创建了 User_Id 字段。这里有什么错误吗？ User 实体中的 HashSet 是否会导致这个额外的 User_Id 字段？

问题：

public class Issue : BaseEntity
{
    [Key]
    public int Id { get; set; }

    //Foreign key for Reporter (User entity)
    public short ReporterId { get; set; }

    //Foreign key for Assignee (User entity)
    public short AssigneeId { get; set; }

    [ForeignKey("ReporterId")]
    public virtual User Reporter { get; set; }

    [ForeignKey("AssigneeId")]
    public virtual User Assignee { get; set; }
}

用户：

public class User : BaseEntity 
{
    [Key]
    public short Id { get; set; }

    public string UserName { get; set; }

    public string Email { get; set; }

    //code omitted for brevity 

    public User()
    {
        Issues = new HashSet<Issue>();
        //code omitted for brevity 
    }        

    public virtual ICollection<Issue> Issues { get; set; }

    //code omitted for brevity 
}

以下是迁移文件中的相关行：

CreateTable(
            "Issue",
            c => new
                {
                    Id = c.Int(nullable: false, identity: true),
                    ReporterId = c.Short(nullable: false),
                    AssigneeId = c.Short(nullable: false),
                    User_Id = c.Short() //???
                })
            .PrimaryKey(t => t.Id)
            .ForeignKey("com.User", t => t.User_Id)  //???
            .ForeignKey("com.User", t => t.AssigneeId)
            .ForeignKey("com.User", t => t.ReporterId)
            .Index(t => t.ReporterId)
            .Index(t => t.AssigneeId)
            .Index(t => t.User_Id);  //???

Answer 1

当您尝试创建多个相同类型的ForeignKey 时，所以 您设置的模型类应如下所示：

public class User : BaseEntity
{
    public User()
    {
        ReporterIssues = new HashSet<Issue>();
        AssigneeIssues = new HashSet<Issue>();
    }

    [Key]
    public short Id { get; set; }
    public string UserName { get; set; }
    public string Email { get; set; }

    // Navigation properties
    public virtual ICollection<Issue> ReporterIssues { get; set; }
    public virtual ICollection<Issue> AssigneeIssues { get; set; }
}

public class Issue : BaseEntity
{
    [Key]
    public int Id { get; set; }
    public short ReporterId { get; set; }
    public short AssigneeId { get; set; }

    // Navigation properties
    public virtual User Reporter { get; set; }
    public virtual User Assignee { get; set; }
}

然后在OnModelCreating配置如下：

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
        base.OnModelCreating(modelBuilder);

        modelBuilder.Entity<User>().HasMany(u => u.AssigneeIssues)
            .WithRequired(i => i.Assignee).HasForeignKey(a => a.AssigneeId)
            .WillCascadeOnDelete(false); // <-- cascade delete must be false

        modelBuilder.Entity<User>().HasMany(u => u.ReporterIssues)
            .WithRequired(i => i.Reporter).HasForeignKey(a => a.ReporterId)
            .WillCascadeOnDelete(false); // <-- cascade delete must be false
 }