使用 Automap 以多对多关系将 ViewModel 映射到 Entity

Question

我有两个实体，它们的关系是多对多的。代码如下：

public class Post : Entity
{
    //public int Id { get; set; }
    public string Title { get; set; }
    public string Body { get; set; }
    public DateTime CreateTime { get; set; }
    public DateTime LastModify { get; set; }

    public ICollection<PostTag> PostTags { get; set; }
    public int AuthorId { get; set; }
    public Author Author { get; set; }
}
public class Tag :Entity
{
    //public int Id { get; set; }
    public string TagName { get; set; }

    public ICollection<PostTag> PostTags { get; set; }
}
public class PostTag :Entity
{
    //public int Id { get; set; }

    public int PostId { get; set; }
    public Post Post { get; set; }
    public int TagId { get; set; }
    public Tag Tag { get; set; }
}
public class PostViewModel
{
    public string Title { get; set; }
    public string Body { get; set; }
    public DateTime CreateTime { get; set; }
    public DateTime LastModify { get; set; }
    public int AuthorId { get; set; }
    public string AuthorName { get; set; }
    public List<TagViewModel> Tags { get; set; }
}

现在，我已经创建了从实体到视图模型的映射配置：

CreateMap<Post, PostViewModel>()
    .ForMember(dest => dest.AuthorId, opt => opt.MapFrom(src => src.Author.Id))
    .ForMember(dest => dest.Tags, opt => opt.MapFrom(src => src.PostTags))
    .ForMember(dest => dest.AuthorName, opt => opt.MapFrom(src => src.Author.User.LastName))
    .ForMember(dest => dest.Body, opt => opt.MapFrom(src => src.Body))
    .ForMember(dest => dest.Title, opt => opt.MapFrom(src => src.Title))
    .ForMember(dest => dest.CreateTime, opt => opt.MapFrom(src => src.CreateTime))
    .ForMember(dest => dest.LastModify, opt => opt.MapFrom(src => src.LastModify))
    .ForMember(dest => dest.Tags, opt => opt.MapFrom(src => src.PostTags.Select(y => y.Tag).ToList()));

我的问题是，当我收到类似以下的 PostViewModel 时：

public async Task<IActionResult> Post([FromBody] PostViewModel postViewModel)
{

}

如何将 PostViewModel 映射到 Post？我想从 PostViewModel 创建一个 Entity 并将它们添加到 DbContext 中，即 post、tag（如果不存在）和 postTag 关系，我该怎么办？

我对 automapper 很陌生，这是我的第一个问题，我希望我做对了，非常感谢您的回答和指导。

Answer 1

我认为你有两个选择。

1) Reverse mapping

您可以将.ReverseMap() 添加到映射配置的末尾

CreateMap<Post, PostViewModel>()
    .ForMember(dest => dest.AuthorId, opt => opt.MapFrom(src => src.Author.Id))
    ...
    .ForMember(dest => dest.Tags, opt => opt.MapFrom(src => src.PostTags.Select(y => y.Tag).ToList()))
    .ReverseMap();

2）您可以为PostViewModel定义一个新的配置Post

CreateMap<PostViewModel, Post>()
    .ForMember(dest => dest.Author.Id, opt => opt.MapFrom(src => src.AuthorId))
    ...etc

然后Mapper.Map<Post>(postViewModel)