Question

我想将POCO映射到ImmutableDictionary<string, object>，而Automapper会引发异常，因为Add不支持ImmutableDictionary操作。

POCO对象位于源类型中名为Data的属性中，该属性将映射到目标中的DataBag属性。目前尚不知道Data的类型。

我正在使用此映射：

var t = new MapperConfiguration(cfg =>
                    cfg.CreateMap(@event.GetType(), typeof(StoredEvent))
                       .ForMember("DataBag", opt => opt.MapFrom("Data")));

并收到此错误：

Mapping types:
Dictionary`2 -> ImmutableDictionary`2
System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] -> System.Collections.Immutable.ImmutableDictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

Destination path:
StoredEvent.DataBag.DataBag.DataBag

为了解决这个问题，我尝试使用自定义解析器：

public class ImmutableDictionaryResolver : IValueResolver
{
    public ResolutionResult Resolve(ResolutionResult source)
    {
        var dictionary = Mapper.Map<Dictionary<string, object>>(source.Value);
        return source.New(dictionary.ToImmutableDictionary());
    }
}

使用此映射：

var t = new MapperConfiguration(cfg =>
            cfg.CreateMap(@event.GetType(), typeof(StoredEvent))
            .ForMember(nameof(StoredEvent.DataBag), opt => 
              opt.ResolveUsing<ImmutableDictionaryResolver>().FromMember("Data")));

但我仍然遇到同样的错误。在第二个例子中，它抱怨：

Mapping types:
ImmutableDictionary`2 -> ImmutableDictionary`2
System.Collections.Immutable.ImmutableDictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]] -> System.Collections.Immutable.ImmutableDictionary`2[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089],[System.Object, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]

Destination path:
StoredEvent.DataBag.DataBag

Answer 1

不要使用ForMember尝试使用ConstructUsing，因此您可以为不可变对象赋予值。

var t = new MapperConfiguration(cfg =>
            cfg.CreateMap(@event.GetType(), typeof(StoredEvent))
            .ConstructUsing(x => new ImmutableDictionaryResolver(...)));

尝试使用AutoMapper映射ImmutableDictionary时出错

1 个答案: