来自多个源字段的自动映射器条件映射 [英] Automapper conditional map from multiple source fields

问题描述

我有一个类似于以下的源类:

I've got a source class like the following:

public class Source
{
    public Field[] Fields { get; set; }
    public Result[] Results { get; set; }
}

并具有一个目标类，如:

And have a destination class like:

public class Destination
{
    public Value[] Values { get; set; }
}

所以我想从EITHER Fields 或 Results 映射到 Values ，具体取决于哪一个不为null(只有一个将具有价值).

So I want to map from EITHER Fields or Results to Values depending on which one is not null (only one will ever have a value).

我尝试了以下地图:

CreateMap<Fields, Values>();                
CreateMap<Results, Values>();                

CreateMap<Source, Destination>()                
            .ForMember(d => d.Values, opt =>
            {
                opt.PreCondition(s => s.Fields != null);
                opt.MapFrom(s => s.Fields });
            })
            .ForMember(d => d.Values, opt =>
            {
                opt.PreCondition(s => s.Results != null);
                opt.MapFrom(s => s.Results);
            });

唯一的问题是，它看起来是否最后一个 .ForMember 映射不满足条件，它会擦除​​第一个映射中的映射结果.

Only issue with this is that it looks if the last .ForMember map doesn't meet the condition it wipes out the mapping result from the first map.

我还考虑过将其作为条件运算符:

I also thought about doing it as a conditional operator:

opt =>opt.MapFrom(s => s.Fields！= null?s.Fields:s.Results)

但是显然它们是不同的类型，所以不要编译.

But obviously they are different types so don't compile.

如何根据条件从不同类型的源属性映射到单个属性?

How can I map to a single property from source properties of different types based on a condition?

谢谢

推荐答案

有一个 ResolveUsing() 方法，该方法可让您进行更复杂的绑定，并且可以使用 IValueResolver 或 Func .像这样:

There is a ResolveUsing() method that allows you for more complex binding and you can use a IValueResolver or a Func. Something like this:

CreateMap<Source, Destination>()
    .ForMember(dest => dest.Values, mo => mo.ResolveUsing<ConditionalSourceValueResolver>());

根据您的需求的价值解析器可能看起来像:

And the value resolver depending on your needs may look like:

 public class ConditionalSourceValueResolver : IValueResolver<Source, Destination, Value[]>
    {
        public Value[] Resolve(Source source, Destination destination, Value[] destMember, ResolutionContext context)
        {
            if (source.Fields == null)
                return context.Mapper.Map<Value[]>(source.Results);
            else
                return context.Mapper.Map<Value[]>(source.Fields);
        }
    }

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