Automapper自定义多对一转换
Automapper自定义多对一转换
提问于 2015-05-18 18:24:05
自动映射器多对一转换
如何将源对象中多个属性的值转换为目标对象中的单个类型？在这种情况下，我可以使用Value Resolvers吗？或者也许有更好的解决方案？
文档
这是来自documentation的example - one to one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
我想将两个对象转换为一个(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;
}
}我想要实现这样的事情：
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;
}
}我知道我可以将整个对象作为源对象传递，但对我来说这不是一个解决方案：
ValueResolver<Document, Currency>我不能使用full object，因为我有许多文档类型，而且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，转换发生在后台(在主主题的转换过程中)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 -使用接口包装一个类：
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;}
}并使用具有以下参数的解析器：
ValueResolver<ICurrencyHolder, Currency>解决方案2 -将元素对象类型作为源元素，并通过反射获取值
ValueResolver<object, Currency>这太可怕了！
回答 3
Stack Overflow用户
发布于 2015-05-25 00:18:04
如果我理解正确的话，您需要执行以下映射:从(CurrencyId，ExchangeRateId)到Currency。您可以使用Tuple (it is a standard .Net class在这些情况下非常方便)来实现它：
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));Stack Overflow用户
发布于 2015-05-21 14:42:47
可能你可以这样映射它：
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 ));也可以：
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>();Stack Overflow用户
发布于 2015-08-01 10:41:04
如果您确定要对每种文档类型执行此操作：
Document document;
var documentDto = Mapper.Map<DocumentDto>(document);然后，您必须为它们中的每一个定义映射。因此，我肯定会采用ICurrencyHolder的想法，并使用如下的解析器：
对解析程序执行操作
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; }
}及其映射：
Mapper.CreateMap<Document, DocumentDto>().ForMember(m => m.Currency, opt => opt.ResolveUsing<CurrencyResolver>());
Mapper.CreateMap<ExtendedDocument, DocumentDto>().ForMember(m => m.Currency, opt => opt.ResolveUsing<CurrencyResolver>());准备就绪后，您可以像这样创建dto，并在映射阶段为您自动解析货币：
var dto = Mapper.Map<DocumentDto>(document);
var extendedDto = Mapper.Map<DocumentDto>(extendedDocument);页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/30300705
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