EF 6当表与自身具有多对多关系时，从DB获取父记录

// 定义实体类
public class Entity
{
    public int Id { get; set; }
    public string Name { get; set; }
    public ICollection<Entity> Parents { get; set; }
    public ICollection<Entity> Children { get; set; }
}

// 配置多对多关系
public class EntityContext : DbContext
{
    public DbSet<Entity> Entities { get; set; }

    protected override void OnModelCreating(DbModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Entity>()
            .HasMany(e => e.Parents)
            .WithMany(e => e.Children)
            .Map(m =>
            {
                m.ToTable("EntityRelationship");
                m.MapLeftKey("ChildId");
                m.MapRightKey("ParentId");
            });
    }
}

// 查询父记录
using (var context = new EntityContext())
{
    var childId = 1;
    var parents = context.Entities
        .Where(e => e.Id == childId)
        .SelectMany(e => e.Parents)
        .ToList();
}