Automapper自定义多对一转换

本文关键字：转换 多对一 自定义 Automapper | 更新日期: 2023-09-27 17:49:29

Automapper多对一转换

如何将源对象中的许多属性值转换为目标对象中的单个类型?我可以在这种情况下使用值解析器吗?或者有更好的解决办法?

下面是文档中的示例- 一对一转换

Mapper.CreateMap<Source, Destination>()
    .ForMember(dest => dest.Total,
        opt => opt.ResolveUsing<CustomResolver>().FromMember(src => src.SubTotal));
Mapper.CreateMap<OtherSource, OtherDest>()
    .ForMember(dest => dest.OtherTotal,
        opt => opt.ResolveUsing<CustomResolver>().FromMember(src => src.OtherSubTotal));
public class CustomResolver : ValueResolver<decimal, decimal> {
// logic here
}

案例

我想把两个对象转换成一个对象(多对一转换)。例如:

public class Document
{
    public int CurrencyId {get; set;}
    public int ExchangeRateId {get; set;}
}
public class DocumentDto
{
    public Currency Currency {get; set;}
}
public class CurrencyDetails
{
    public Currency Currency {get; private set;}
    public ExchangeRate ExchangeRate {get; private set;}
    public CurrencyDetails(Currency currency, ExchangeRate exchangeRate)
    {
        Currency = currency;
        ExchangeRate = exchangeRate;
    }
}

我想实现这样的事情:

public class CurrencyResolver : ValueResolver<int, int, CurrencyDetails>
{
    protected override Currency ResolveCore(int currencyId, int exchangeRateId)
    {
        var currency = new Currency(currencyId); //simplified logic
        var exchangeRate = new ExchangeRate(exchangeRateId);
        var currencyDetails = new CurrencyDetails(currency, exchangeRate);
        return currencyDetails;
    }
}

我知道我可以传递整个对象作为源对象，但对我来说这不是一个解决方案:

ValueResolver<Document, Currency>

我不能使用完整对象，因为我有很多文档类型，我不想为每个文档创建新的解析器。在我的例子中，也不允许忽略元素(用于手动转换)。货币转换逻辑必须由AutoMapper执行。

对我来说，转换发生在背景中(在主体转换期间)是很重要的。

例如:

Document document;
var documentDto = Mapper.Map<DocumentDto>(document); // and in this moment i have proper CurrencyDetails object!

谢谢你的建议。

我的解决方案

我想出了两个解决方案，但我不喜欢它们(太脏了)

解决方案1 -用接口包装一个类:

public interface ICurrencyHolder
{
    int CurrencyId {get; set;}
    int ExchangeRateId {get; set;}
}
public class Document : ICurrencyHolder
{
    public int CurrencyId {get; set;}
    public int ExchangeRateId {get; set;}
}

并使用下列参数的解析器:

ValueResolver<ICurrencyHolder, Currency>

方案2 -作为源元素对象类型，通过反射获取值

ValueResolver<object, Currency>

这太可怕了!

Automapper自定义多对一转换

如果我理解正确，您需要做以下映射:从(CurrencyId, ExchangeRateId)到Currency。您可以使用Tuple实现它(它是一个标准的。net类，在这些情况下非常方便):

Mapper.CreateMap<Tuple<int,int>, Currency>()
   .ForMember(x => x.Currency, cfg => cfg.MapFrom(y => new Currency(y.Item1, y.Item2));

按如下方式调用映射器:

Mapper.Map<Tuple<int,int>, Currency>(Tuple.Create(doc.CurrencyId, doc.ExchangeRateId));

也许你可以这样映射:

Mapper.CreateMap<Source, Destination>()
      .ConstructUsing(s => Mapper.Map<Source, Currency>(s));
Mapper.CreateMap<Source, Currency>()
      .ForMember(dst => dst.CurrencySymbol, map => map.MapFrom(src => src.DocumentDto.CurrencySymbol))
      .ForMember(dst => dst.ExchangeRate , map => map.MapFrom(src => src.Document.ExchangeRate ));
也可能

: 

Mapper.CreateMap<Source, Destination>()
      .ConstructUsing(s => Mapper.Map<Source, Currency>(s));
Mapper.CreateMap<Source, Currency>()
      .ConstructUsing(s => Mapper.Map<DocumentDto, Currency>(s))
      .ConstructUsing(s => Mapper.Map<Document, Currency>(s));
Mapper.CreateMap<DocumentDto, Currency>();
Mapper.CreateMap<Document, Currency>();

如果您确定每个文档类型都要这样做:

Document document;
var documentDto = Mapper.Map<DocumentDto>(document);

那么您必须为它们中的每一个定义映射。所以我肯定会使用ICurrencyHolder的想法并使用像这样的解析器:

解析器

public class CurrencyResolver : ValueResolver<ICurrencyHolder, Currency>
{
    protected override Currency ResolveCore(ICurrencyHolder source)
    {
        return new Currency(source.CurrencyId, source.ExchangeRateId);
    }
}

文档"类型"

public class Document : ICurrencyHolder
{
    public int CurrencyId { get; set; }
    public int ExchangeRateId { get; set; }
}
public class ExtendedDocument : ICurrencyHolder
{
    public DateTime SomeDate { get; set; }
    public int CurrencyId { get; set; }
    public int ExchangeRateId { get; set; }
}
public interface ICurrencyHolder
{
    int CurrencyId { get; set; }
    int ExchangeRateId { get; set; }
}

和映射:

Mapper.CreateMap<Document, DocumentDto>().ForMember(m => m.Currency, opt => opt.ResolveUsing<CurrencyResolver>());
Mapper.CreateMap<ExtendedDocument, DocumentDto>().ForMember(m => m.Currency, opt => opt.ResolveUsing<CurrencyResolver>());

你可以像这样创建你的dto，并在映射阶段为你获得货币解析:

var dto = Mapper.Map<DocumentDto>(document);
var extendedDto = Mapper.Map<DocumentDto>(extendedDocument);
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