public class Category
{public Category(){Id = GuidComb.GenerateComb();}public Guid Id { get; set; }public string Name { get; set; }public string Description { get; set; }public virtual IList<Topic> Topics { get; set; }
}public class Topic
{public Topic(){Id = GuidComb.GenerateComb();}public Guid Id { get; set; }public string Name { get; set; }public DateTime CreateDate { get; set; }public virtual Category Category { get; set; }
}public class CategoryMapping : EntityTypeConfiguration<Category>
{public CategoryMapping(){HasKey(x => x.Id);HasMany(x => x.Topics).WithRequired(x => x.Category);}
}public class TopicMapping : EntityTypeConfiguration<Topic>
{public TopicMapping(){HasKey(x => x.Id);HasRequired(t => t.Category).WithMany(t => t.Topics).Map(m => m.MapKey("Category_Id")); // 注意：如果实体中保存外键属性，那么这样写：this.HasRequired(t => t.Category).WithMany(t => t.Topics).HasForeignKey(m => m.Category_Id);
            }
}

public class TopicTag
{public TopicTag(){Id = GuidComb.GenerateComb();}public Guid Id { get; set; }public string Tag { get; set; }public virtual IList<Topic> Topics { get; set; }
}public class Topic
{public Topic(){Id = GuidComb.GenerateComb();}public Guid Id { get; set; }public string Name { get; set; }public DateTime CreateDate { get; set; }public virtual IList<TopicTag> Tags { get; set; }
}public class TopicTagMapping : EntityTypeConfiguration<TopicTag>
{public TopicTagMapping(){HasKey(x => x.Id);}
}public class TopicMapping : EntityTypeConfiguration<Topic>
{public TopicMapping(){HasKey(x => x.Id);HasMany(t => t.Tags).WithMany(t => t.Topics).Map(m =>{m.ToTable("Topic_Tag");m.MapLeftKey("TopicTag_Id");m.MapRightKey("Topic_Id");});}
}