automapper unflatten从父对象中排除值 [英] automapper unflatten excludes value from parent object

问题描述

当我更新子表中的一行时，实体框架核心(2.0)正在对父表执行其他工作.我已经查明原因是未在AutoMapper生成的未展平的对象树中设置一个值(我并不是说这是AutoMapper中的错误；这可能与我的代码有更多关系).

I've a situation where entity framework core (2.0) is performing additional work to a parent table when I update a row in a child table. I've pin-pointed the cause to a value not being set in the unflattened object tree produced by AutoMapper (I'm not saying it is an error in AutoMapper; it's probably more to do with my code).

我正在使用ASP.NET Core 2.0，C#，EF Core 2.0和AutoMapper进行API开发.该数据库已经存在，并且EF类已经从该数据库中被搭建起来.

I'm using ASP.NET Core 2.0, C#, EF Core 2.0 and AutoMapper for the API development side. The database already exists and the EF classes scaffolded from it.

为简短起见，子表为Note，父表为NoteType. EF类(删除了外部列)如下:

To keep it short, the child table is Note and the parent table is NoteType. The EF classes (extraneous columns removed) are as follows :

//Entity classes
public partial class Note
    {
        public int NoteBookId { get; set; }
        public short NoteSeqNo { get; set; }
        public short NoteTypeId { get; set; }
        public string NoteText { get; set; }

        public NoteBook NoteBook { get; set; }
        public NoteType NoteType { get; set; }
    }

public partial class NoteType
    {
        public NoteType() { Note = new HashSet<Note>(); }
        public short NoteTypeId { get; set; }
        public string NoteTypeDesc { get; set; }
        public ICollection<Note> Note { get; set; }
    }

//DTO class
    public class NoteDto
    {
        public int NoteBookId { get; set; }
        public short NoteSeqNo { get; set; }
        public short NoteTypeId { get; set; }
        public string NoteTypeNoteTypeDesc { get; set; }
        public string NoteText { get; set; }
    }

 public class NoteTypeDto
    {
        public short NoteTypeId { get; set; }
        public string NoteTypeDesc { get; set; }
    }

• (NoteBookId + NoteSeqNo)是Note的主键.
• NoteTypeId是NoteType的主键.

配置

这是AutoMapper配置:

This is the AutoMapper configuration:

// config in startup.cs
config.CreateMap<Note,NoteDto>().ReverseMap();
config.CreateMap<NoteType,NoteTypeDto>().ReverseMap();

读取数据

作为数据检索的结果，我得到了预期的结果，并且填充了父注释类型描述.

As a result of data retrieval I get the expected result and the parent note type description is populated.

// EF get note in repository
            return await _dbcontext.Note
                .Where(n => n.NoteId == noteId && n.NoteSeqNo == noteSeqNo)
                .Include(n => n.NoteType)
                .FirstOrDefaultAsync();

// Get note function in API controller
                Note note = await _repository.GetNoteAsync(id, seq);
                NoteDto noteDto = Mapper.Map<NoteDto>(note);

示例JSON结果:

{
    "noteBookId": 29,
    "noteSeqNo": 19,
    "noteTypeId": 18,
    "noteTypenoteTypeDesc": "ABCDE",
    "noteText": "My notes here."
}

更新数据

在更新过程中逆转过程时，API控制器会将dto映射到实体

When the process is reversed during an update, the API controller maps the dto to the entity

Mapper.Map<Note>(noteDto)

然后，当存储库代码将其传递给EF时，EF尝试添加ID为0的NoteType行.未展平的对象树如下所示:

Then when it is passed to EF by the repository code, EF tries to add a NoteType row with id 0. The unflattened object tree looks like this:

Note
    NoteBookId = 29
    NoteSeqNo = 19
    NoteTypeId = 18
    NoteTypeNoteTypeDesc = "ABCDE"
    NoteText = "My notes updated."
    NoteType.NoteTypeDesc = "ABCDE"
    NoteType.NoteTypeId = 0

父ID列(NoteType.NoteTypeId)的值为0，并且未分配18的值，这是我期望的值.

The parent id column (NoteType.NoteTypeId) value is 0 and is not assigned the value of 18 which is what I expected.

(在调试过程中，我将NoteType.NoteTypeId手动设置为18，以确保EF对其不执行任何操作.)

(During debugging I manually set NoteType.NoteTypeId to 18 to ensure EF did nothing with it).

要解决此问题，我现在将存储库代码中注释"中的NoteType无效.

To work around this at the moment I nullify the NoteType in the Note in the repository code.

我应该让AutoMapper用setter填充所有父属性，还是错过一些配置?也许我的方法存在明显的缺陷?

Should I expected AutoMapper to populate all the parent properties with setters or have I missed some configuration? Perhaps there is a glaring flaw in my approach?

推荐答案

当AutoMapper反转映射时，它必须从平面对象收集嵌套对象的所有信息.您的DTO仅携带映射NoteType -> NoteTypeDesc的值.不是NoteType -> NoteTypeId，因此AM确实不知道从何处获得该价值.

When AutoMapper reverses the mapping, it has to collect all information for nested objects from the flat object. Your DTO only carries a value for the mapping NoteType -> NoteTypeDesc. Not for NoteType -> NoteTypeId, so AM really doesn't have any idea where to get that value from.

如果您只想依靠拼合，唯一的更改方法是在DTO上添加除拼合之外的拼合NoteTypeId:

If you want to rely on flattening only, the only way to change that is to add a flattened NoteTypeId to the DTO besides the unflattened one:

public class NoteDto
{
    public int NoteBookId { get; set; }
    public short NoteSeqNo { get; set; }
    public short NoteTypeId { get; set; } // Not flattened
    public short NoteTypeNoteTypeId { get; set; } // Flattened
    public string NoteTypeNoteTypeDesc { get; set; }
    public string NoteText { get; set; }
}

另一种方法是将其添加到您的映射中:

The alternative is to add this to your mapping:

config.CreateMap<Note, NoteDto>()
    .ForMember(dest => dest.NoteTypeId,
        e => e.MapFrom(src => src.NoteType.NoteTypeId))
    .ReverseMap();

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