Question

我在 .Core 项目中有2个名为News和NewsAttachment的实体。这些实体通过News_Id建立了关系。换句话说，当我创建新的News并将其添加到数据库中时，此News可能有一个或两个附件媒体，我想在名为NewsAttachment的相关表中插入。所以我可能想要检索News_Id并在相关表中插入附件。

我在NewsDto中定义了名为CreateNewsDto和NewsAppService的2个DTO，并通过CreateNewsDto插入新的News，但我不知道该怎么做它适用于NewsAttachment。

这是我的News实体：

public class News : FullAuditedEntity<long>
{
    public const int MaxTitleLength = 150;
    public const int MaxContentLength = 1200;
    public const int MaxMetaTagLength = 60;

    [Required]
    [MaxLength(MaxTitleLength)]
    public string Title { get; set; }

    [Required]
    public string Code { get; set; }

    [Required]
    [MaxLength(MaxContentLength)]
    public string Content { get; set; }

    public DateTime PublishDate { get; set; }

    [MaxLength(MaxMetaTagLength)]
    public string Tags { get; set; }

    public virtual NewsType Type { get; set; }

    public virtual ICollection<NewsAttachment> Attachments { get; set; }
}

和NewsAttachment实体：

public class NewsAttachment: FullAuditedEntity<long>
{
    public const int MaxTitleLength = 50;

    [Required]
    [MaxLength(MaxTitleLength)]
    public string FileName { get; set; }

    [Required]
    public byte[] File { get; set; }
    public string FileExtension { get; set; }
    public int FileSize { get; set; }

    [Required]
    public DateTime RegisterDate { get; set; }

    public virtual News News { get; set; }
}

和DTO：

public class NewsDto : EntityDto<long>
{
    public const int MaxTitleLength = 50;
    public const int MaxContentLength = 800;
    public const int MaxMetaTagLength = 60;

    [Required]
    [MaxLength(MaxTitleLength)]
    public string Title { get; set; }

    [Required]
    public string Code { get; set; }

    [Required]
    [MaxLength(MaxContentLength)]
    public string Content { get; set; }

    public DateTime PublishDate { get; set; }

    [MaxLength(MaxMetaTagLength)]
    public string Tags { get; set; }

    public virtual NewsType Type { get; set; }
}

和

public class CreateNewsDto
{
    public const int MaxTitleLength = 50;
    public const int MaxContentLength = 800;
    public const int MaxMetaTagLength = 60;

    [Required]
    [MaxLength(MaxTitleLength)]
    public string Title { get; set; }

    [Required]
    public string Code { get; set; }

    [Required]
    [MaxLength(MaxContentLength)]
    public string Content { get; set; }

    public DateTime PublishDate { get; set; }

    [MaxLength(MaxMetaTagLength)]
    public string Tags { get; set; }

    public virtual NewsType Type { get; set; }

    public virtual ICollection<NewsAttachment> Attachments { get; set; }
}

以下是NewsAppService中我推荐的插入新News并将相关媒体添加到NewsAttachment表格的推定方法：

public virtual NewsDto InsertWithMedia(CreateNewsDto input, NewsAttachmentDto attach)
{
   var news = ObjectMapper.Map<NewsManagement.News>(input);

    var newsAttachment = ObjectMapper.Map<NewsAttachment>(attach);
    newsAttachment.News.Id = news.Id;
    return MapToEntityDto(news);
}

Answer 1

两种选择：

添加到ICollection并让EF处理实体：

public virtual NewsDto InsertWithMedia(CreateNewsDto input, NewsAttachmentDto attach)
{
    var news = ObjectMapper.Map<NewsManagement.News>(input);
    news.Attachments = new List<NewsAttachment>(); // 1

    var newsAttachment = ObjectMapper.Map<NewsAttachment>(attach);
    news.Attachments.Add(newsAttachment);          // 2

    _newsRepository.Insert(news);                  // 3
    CurrentUnitOfWork.SaveChanges();               // 4

    return MapToEntityDto(news);
}

使用外键添加Id代替集合：

public class NewsAttachment: FullAuditedEntity<long>
{
    // ...

    public virtual long NewsId { get; set; }
    public virtual News News { get; set; }
}

public virtual NewsDto InsertWithMedia(CreateNewsDto input, NewsAttachmentDto attach)
{
    var news = ObjectMapper.Map<NewsManagement.News>(input);
    var newsId = _newsRepository.InsertAndGetId(news); // 1

    var newsAttachment = ObjectMapper.Map<NewsAttachment>(attach);
    newsAttachment.NewsId = newsId;                    // 2

    _newsAttachmentRepository.Insert(newsAttachment);  // 3
    CurrentUnitOfWork.SaveChanges();                   // 4

    return MapToEntityDto(news);
}

第二个适用于更新 - 当newsId已知时 - 如果NewsDto也有Attachments（应该是ICollection<AttachmentDto>类型），则可能需要执行其他步骤。

Answer 2

谢谢@aaron。毕竟，我有一点问题。在 .WebMpa 项目中如何检索相关图片的新闻。我在模型文件夹中定义NewsViewModel并使用Auto Mapper库将此ViewModel映射到NewsDto。在NewsController中调用NewsAppService和GetAll方法从数据库获取新闻。对于这种情况，我有2个场景： 1-我认为在 .Application 项目中更改此方法并添加一些linq查询以从NewsAttachment获取包含相关图片的新闻 2-所有关于News和NewsAttachment的操作以及与两个实体一起加入 .WebMpa 项目和NewsController。我真的很困惑。你能帮我展示一下这个例子吗？

如何在Application Layer中实现使用子集合创建？

2 个答案: