entity-framework - EF Core 2.0 迁移 - 具有附加字段的多对多

Question

我正在使用 EF Core 2.0 并创建了与联接实体的多对多关系。当我添加新的迁移 EF 时，总是会创建一个额外的索引/Id 字段，这是完全愚蠢的。这是我的加入实体:

public class Team_Member
{
    public int TeamId { get; set; }
    public Team Team { get; set; }

    public int MemberId { get; set; }
    public Member Member { get; set; }

    public MemberTypeEnum MemberType { get; set; }
}

这是连接表的配置(遵循互联网上的几个示例):

public class Team_MemberConfig : IEntityTypeConfiguration<Team_Member>
{
    public void Configure(EntityTypeBuilder<Team_Member> builder)
    {
        builder.ToTable("Team_Member");
        builder.HasKey(tm => new { tm.TeamId, tm.MemberId });
        builder.HasOne<Team>()
            .WithMany(t => t.Team_Member)
            .HasForeignKey(tm => tm.TeamId)
            .OnDelete(DeleteBehavior.Restrict);
        builder.HasOne<Member>()
            .WithMany(m => m.Team_Member)
            .HasForeignKey(tm => tm.MemberId)
            .OnDelete(DeleteBehavior.Restrict);
    }
}

对于每个外键列，迁移都会添加第二个外键列:

columns: table => new
            {
                TeamId = table.Column<int>(nullable: false),
                MemberId = table.Column<int>(nullable: false),
                **MemberId1** = table.Column<int>(nullable: true),
                MemberType = table.Column<int>(nullable: false),
                **TeamId1** = table.Column<int>(nullable: true)
            },

和两个完全相同的约束:

table.ForeignKey(
                    name: "FK_Team_Member_Member_MemberId",
                    column: x => x.MemberId,
                    principalTable: "Member",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Restrict);
                table.ForeignKey(
                    name: "FK_Team_Member_Member_MemberId1",
                    column: x => x.MemberId1,
                    principalTable: "Member",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Restrict);
                table.ForeignKey(
                    name: "FK_Team_Member_Team_TeamId",
                    column: x => x.TeamId,
                    principalTable: "Team",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Restrict);
                table.ForeignKey(
                    name: "FK_Team_Member_Team_TeamId1",
                    column: x => x.TeamId1,
                    principalTable: "Team",
                    principalColumn: "Id",
                    onDelete: ReferentialAction.Restrict);

我在这里做错了什么？

Answer 1

任何时候您看到 EF(核心)生成额外的 FK 列，都清楚地表明由于使用了错误的流畅 API 重载而导致未映射的引用或集合导航属性。所有相关的 Fluent API(HasOne、HasMany、WithOne、WithMany)都具有带导航属性且不带导航属性的重载。当相应的实体没有导航时，您必须使用第一个，并且您应该使用精确表示相应实体中是否存在导航属性。如果不这样做，就会留下未映射的导航属性，并且 EF 会创建其他关系。

就您的情况而言，两个差异(标记为 A、B)介于:

public class Team_Member
{
    public int TeamId { get; set; }
    public Team Team { get; set; } // <-- A

    public int MemberId { get; set; }
    public Member Member { get; set; } // <-- B

    public MemberTypeEnum MemberType { get; set; }
}

和

builder.HasOne<Team>() // <-- A
    .WithMany(t => t.Team_Member)
    .HasForeignKey(tm => tm.TeamId)
    .OnDelete(DeleteBehavior.Restrict);
builder.HasOne<Member>() // <-- B
    .WithMany(m => m.Team_Member)
    .HasForeignKey(tm => tm.MemberId)
    .OnDelete(DeleteBehavior.Restrict);

如前所述，只需使它们匹配即可:

builder.HasOne(tm => tm.Team) // <-- A
    .WithMany(t => t.Team_Member)
    .HasForeignKey(tm => tm.TeamId)
    .OnDelete(DeleteBehavior.Restrict);
builder.HasOne(tm => tm.Member) // <-- B
    .WithMany(m => m.Team_Member)
    .HasForeignKey(tm => tm.MemberId)
    .OnDelete(DeleteBehavior.Restrict);

问题就解决了。