c# - Entity Framework 多对多关系表创建 "backwards"

Question

我遇到了 EF6 和多对多关系的问题。我有以下设置:

public class Foo
{
    public int Id { get; set; }
    public virtual ICollection<Bar> Bars { get; set; }
    public virtual ICollection<SubBar> SubBars { get; set; }

    public Foo()
    {
        Bars = new HashSet<Bar>();
        SubBars = new HashSet<SubBar>();
    }
}

public class Bar
{
    public int Id { get; set; }
    public virtual ICollection<Foo> Foos { get; set; }

    public Bar()
    {
        Foos = new HashSet<Foo>();
    }
}

public class SubBar
{
    public int Id { get; set; }
    public virtual ICollection<Foo> Foos { get; set; }

    public SubBar()
    {
        Foos = new HashSet<Foo>();
    }
}

Foo 和Bar 之间的关系正常工作，并且在数据库中有一个名为BarFoos 的表。然而 Foo 和 SubBar 之间的关系是相反的。数据库中有一个名为 FooSubBars 的表，它基本上保持正确的关系，但需要预先加载，如 SubBar.AsQueryable().Include(sb => sb.Foos)返回带有消息 Invalid object name dbo.SubBarFoos 的 EntityCommandExecutionException。

问题是:如何反转关系表名称以允许预先加载？
--编辑--
迁移中的DB创建如下:

CreateTable(
            "dbo.BarFoos",
            c => new
                {
                    Bar_Id = c.Int(nullable: false),
                    Foo_Id = c.Int(nullable: false),
                })
            .PrimaryKey(t => new { t.Bar_Id, t.Foo_Id })
            .ForeignKey("dbo.Bars", t => t.Bar_Id, cascadeDelete: true)
            .ForeignKey("dbo.Foos", t => t.Foo_Id, cascadeDelete: true)
            .Index(t => t.Bar_Id)
            .Index(t => t.Foo_Id);

CreateTable(
            "dbo.FooSubBars",
            c => new
                {
                    Foo_Id = c.Int(nullable: false),
                    SubBar_Id = c.Int(nullable: false),
                })
            .PrimaryKey(t => new { t.Foo_Id, t.SubBar_Id })
            .ForeignKey("dbo.Foos", t => t.Foo_Id, cascadeDelete: true)
            .ForeignKey("dbo.SubBars", t => t.SubBar_Id, cascadeDelete: true)
            .Index(t => t.Foo_Id)
            .Index(t => t.SubBar_Id);

替换迁移中的表名就足够了吗？

Answer 1

如果您重写 DbContext 上的 OnModelCreating 方法，则可以确保生成的表名称为“FooBars”，如下所示:

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

    modelBuilder.Entity<Foo>().HasMany(f => f.Bars).WithMany(b => b.Foos)
            .Map(m => 
                m.ToTable("FooBars")
                // Optionally specify the key column names...
                .MapLeftKey("FooId") 
                .MapRightKey("BarId")
            );

    modelBuilder.Entity<Foo>().HasMany(f => f.SubBars).WithMany(sb => sb.Foos).Map(m => m.ToTable("FooSubBars"));
}

这将在迁移中产生这个:

        CreateTable(
            "dbo.FooBar",
            c => new
                {
                    FooId = c.Int(nullable: false),
                    BarId = c.Int(nullable: false),
                })
            .PrimaryKey(t => new { t.FooId, t.BarId })
            .ForeignKey("dbo.Foos", t => t.FooId, cascadeDelete: true)
            .ForeignKey("dbo.Bars", t => t.BarId, cascadeDelete: true)
            .Index(t => t.FooId)
            .Index(t => t.BarId);

        CreateTable(
            "dbo.FooSubBar",
            c => new
                {
                    Foo_Id = c.Int(nullable: false),
                    SubBar_Id = c.Int(nullable: false),
                })
            .PrimaryKey(t => new { t.Foo_Id, t.SubBar_Id })
            .ForeignKey("dbo.Foos", t => t.Foo_Id, cascadeDelete: true)
            .ForeignKey("dbo.SubBars", t => t.SubBar_Id, cascadeDelete: true)
            .Index(t => t.Foo_Id)
            .Index(t => t.SubBar_Id);

我还尝试在 DbContext 上查询 SubBars 时预先加载 Foos，但没有出现任何错误:

var context = new FooBarContext();

var subBars = from sb in context.SubBars.Include(i => i.Foos)
              select sb;